BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from
Differences in the pregnancy gestation period and mean birthweights in infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton: A retrospective analysis of routinely collected data.
For peer review only Journal: BMJ Open
Manuscript ID bmjopen-2017-017139
Article Type: Research
Date Submitted by the Author: 03-Apr-2017
Complete List of Authors: Garcia, Rebecca; University of Bedfordshire, Institute for Health Research Ali, Nasreen; University of Bedfordshire Faculty of Health and Social Sciences, Institute for Health Research Guppy, Andy; University of Bedfordshire, Department of Psychology Griffiths, Malcolm; 3Luton &Dunstable University Hospital NHS Foundation Trust, Obsetrics Randhawa, Gurch; University of Bedfordshire, Institute for Health Research
Primary Subject Health services research Heading:
Secondary Subject Heading: Obstetrics and gynaecology, Public health http://bmjopen.bmj.com/ Keywords: Low birthweight, Pakistani, South Asian, Bangladeshi, Indian
on October 1, 2021 by guest. Protected copyright.
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 1 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Differences in the pregnancy gestation period and mean birthweights in 4 5 infants born to Indian, Pakistani, Bangladeshi and white British mothers in 6 Luton: A retrospective analysis of routinely collected data. 7 8 Rebecca Garcia1, #, Nasreen Ali1, Andy Guppy 2, Malcolm Griffiths3, Gurch Randhawa1 9 10 11 12 1 The Institute For Health Research, 2 The Institute for Applied Social Sciences, University of 13 Bedfordshire, Putteridge Bury, Hitchin Road, Luton, Bedfordshire, LU2 8LE. 14 15 3 Luton &DunstableFor University peer Hospital NHS review Foundation Trust, Lewsey only Rd, Luton, LU4 0DZ 16 17 #corresponding author 18 19 Telephone 01582 743744 20 21 22 23 Email addresses: 24 25 RG: [email protected] 26 27 NA: [email protected] 28 AG: [email protected] 29 30 MG: [email protected] 31 GR: [email protected] 32 33
34 http://bmjopen.bmj.com/ 35 36 37 Keywords: low birthweight, gestation, south Asian, Pakistani, Indian Bangladeshi 38 39 40 41 Word count 42 on October 1, 2021 by guest. Protected copyright. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 2 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Objective 4 5 To compare mean birthweights and gestational age at delivery of infants born to Indian, 6 Pakistani, Bangladeshi and white British mothers in Luton, UK. 7 8 Design 9 10 11 Retrospective analysis using routinely recorded secondary data in Ciconia Maternity 12 information System (CMiS), between 2008 and 2013. 13 14 15 Setting: For peer review only 16 17 Luton, UK 18 19 Participants 20 21 Mothers whose ethnicity was recorded as white British, Bangladeshi, Pakistani or Indian and 22 living in Luton, aged over 16, who had a live singleton birth over 24 weeks of gestation were 23 24 included in the analysis (N= 14,871). 25 26 Outcome measures 27 28 Primary outcome measures were mean birthweight and gestational age at delivery 29 30 Results 31 32 After controlling for maternal age, smoking, diabetes, gestation age, parity and maternal 33 height and BMI at booking, a significant difference in infants mean birthweight was found
34 between white British and Indian, Pakistani and Bangladeshi infants, F(3, 12287) = 300.32, http://bmjopen.bmj.com/ 35 p<.0005. The partial Eta squared for maternal ethnicity was 2= .067. The adjusted mean 36 birthweight for white British infants was found to be 3377.89g (95% CI 3365.34 3390.44), 37 38 Indian infants 3033.09g (95% CI 3038.63 3103.55), Pakistani infants 3129.49g(95% CI 39 3114.5 3144.48) and Bangladeshi infants 3064.21g (95% CI 3041.36 3087.06. There was a 40 significant association in pre term delivery found in primapara Indian mothers (χ2 (3) = 9.9, 41 p = .019). 42 43 on October 1, 2021 by guest. Protected copyright. 44 Conclusions 45 46 Results show important differences in adjusted mean birthweight between Indian, Pakistani, 47 Bangladeshi and white British women. Moreover, an association was found between 48 primapara Indian mothers and pre term delivery, when compared with Pakistani, Bangladeshi 49 and white British women. 50 51 52 53 54 55 56 57 58 59 60 2
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 3 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Strengths and Limitations of the study 4 • Using routinely collected data over six years, this study shows important differences 5 6 in birthweight at delivery between Indian, Pakistani Bangladeshi and white British 7 8 women. 9 • A significant association was found between pre term delivery and primapara Indian 10 11 mothers. 12 13 • This paper adds to the sparse existing evidence which examines heterogeneity in 14 birthweight and gestation age at delivery between women from South Asia in the UK. 15 For peer review only 16 • A large sample size was used (N=14,871), providing more generalisable results 17 18 19 20 21 22 23 Introduction 24 Low birthweight (LBW) is a significant contributory factor for increased risk of infant 25 26 mortality and morbidity[1], and has health consequences extending into adulthood[2].It is 27 28 also a recognised proxy for maternal health[3,4]. LBW is defined as birthweight of less than 29 30 31 2500g at birth[5,6]. The rather arbitrary figure of 2500g was determined by the World Health 32 33 Organisation, as birthweight less than this shows a substantially increased mortality rate[7].
34 http://bmjopen.bmj.com/ 35 Birthweight of 1500 g is classified as very low birthweight (VLBW) and has an exponentially 36 37 higher mortality rate[8]. V/LBW may be a consequence of a number of mediating factors 38 39 including pre term birth (PTB)[9], small for gestational age (SGA)[6,10] and intrauterine 40 41 42 growth restriction (IUGR), whereby the normal development of the fetus is hampered[11]. 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 Existing evidence shows that South Asian women typically give birth to infants of lower 47 48 birthweights than white British women[12,13] with babies on average being 230 350g 49 50 51 lighter[14–16]. Typically, statistics in the UK uses aggregated data from Indian, Pakistani 52 53 and Bangladeshi infants/mothers, as ‘South Asian’[4,17–19]; obscuring nuances between 54 55 each ethnic group[20], or have been reported as ‘South Asian’ when only one specific ethnic 56 57 group is reported (e.g. Pakistani) [16,19]. Research documents a host of maternal, infant and 58 59 60 3
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 4 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 social factors contributing to LBW, for example; gestational age at delivery [21] poor 4 5 maternal nutrition[22], smoking[23], maternal underweight[24], socioeconomic status[5], and 6 7 maternal depression[25]. Studies have also assessed differences in maternal country of birth 8 9 10 on birthweights[14,26], and between generations[4,14,27]. 11 12 13 14 Lighter birthweight infants in South Asian infants are well documented[12,14,19]. Margetts 15 For peer review only 16 and colleagues[4], defined South Asian mothers originating from the Indian sub continent 17 18 19 using either maternal place of birth e.g. India, Pakistan or Bangladesh (as first generation) or 20 21 UK born (as second generation). They reported differences in the mean birthweights of first 22 23 generation Indian (3077g), Bangladeshi (3161g) and Pakistani (3235g) infants. The same 24 25 trend was observed in the Millennium Cohort Study (MCS) whereby Indian mothers have the 26 27 lightest infants and Pakistani mothers had the heaviest[12]. Conversely, Leon and 28 29 30 Moser[14]found Bangladeshi infants were the lightest, while consistent with the other 31 32 studies; Pakistani infants were heaviest among the infants born to South Asian mothers. 33
34 http://bmjopen.bmj.com/ 35 36 Margetts et al[4] restricted their analyses to births after thirty seven weeks, which eliminated 37 38 39 trends accounted for by gestational age, in addition to aggregating maternal ethnicity to 40 41 assess for differences between maternal generations (i.e. born in the Indian Subcontinent 42 43 classified as first generation or UK classified as second generation). While the MCS showed on October 1, 2021 by guest. Protected copyright. 44 45 that Pakistani mothers had a lower rate of pre term delivery, the study showed that Indian 46 47 mothers had a higher rate[12]. Moreover, national figures for 2012 showed Bangladeshi 48 49 50 mothers had higher rate of infant mortality, conversely, Pakistani and Indian mothers had 51 52 higher preterm delivery rates[28] while Pakistani mothers had a higher preterm delivery 53 54 mortality rate, when compared to British women[29]. Together this demonstrates discreet 55 56 differences between birth patterns of women of South Asian ethnicity in the UK. 57 58 59 60 4
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 5 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 4 5 LBW is a complex research area that has been hampered by inconsistent research methods 6 7 and outcome measures such as mean birthweight[4,14], or weight frequencies [3,30,31], or 8 9 10 aggregated ethnicities[4], thereby making comparison between studies difficult. It is 11 12 important to tease out the nuances of low birthweight trends between Indian, Pakistani and 13 14 Bangladeshi mothers in order to uncover modifiable factors before specific tailored 15 For peer review only 16 interventions are developed[32] and by identifying differences in birthweight and gestational 17 18 19 age at delivery between Indian, Pakistani and Bangladeshi and white British women in Luton, 20 21 England this paper makes a contribution to this research area. 22 23 24 25 26 27 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 6 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Methods 4 5 Routinely collected retrospective data from Ciconia Maternity information System (CMiS) 6 7 from the Luton and Dunstable University Hospital was used. The CMiS database is a clinical 8 9 information system used in some maternity departments in the UK to record all births (i.e. 10 11 hospital and home). Purposive sampling of women aged over 16 and all birth outcomes (i.e. 12 13 14 live and perinatal mortality), who gave birth between January 2008 and December 2013, 15 For peer review only 16 residing in specified postcode areas were included. 17 18 19 Variables: 20 21 Outcome variables of mean birthweight and pre term gestation age were used. Known 22 23 confounders were maternal age (16 20, 21 25, 26 30, 31 35, 36 40, >40), smoking (binary 24 25 variable smoker/non smoker), parity, diabetes (binary variable), gestation age (binary 26 27 28 variable <24 weeks of gestation excluded, 24 37 weeks of gestation and after 37 weeks of 29 30 gestation) and maternal height and BMI at booking were included and controlled [31,33–36]. 31 32 Maternal hypertension is associated with increased risks of adversity in pregnancy for mother 33
34 and fetus, including placental problems and intrauterine growth restriction[37]. However, the http://bmjopen.bmj.com/ 35 36 37 CMiS data (for white British, Indian, Pakistani and Bangladeshi records) only had 12 data 38 39 entries recorded for maternal hypertension; the reasons for the lack of data are unknown and 40 41 therefore to avoid error, the variable was excluded from this analysis. 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 Recording ethnicity in the NHS is a mandatory requirement and staff are required to ask 47 48 49 women for their self ascribed ethnicity, according to the 2001 census categories[38] Ethnicity 50 51 is a self defined construct, which incorporates culture, religion, shared language and 52 53 ancestry[39]. Consequently, within this study, maternal country of birth, length of residency 54 55 or generational status was not ascertained, but the broader self classification of ethnicity as 56 57 recorded in the NHS are used for analysis. Cases with missing data were excluded. 58 59 60 6
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 7 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Statistical analysis: 4 5 Analyses were conducted using IBM Statistics Package for the Social Sciences (SPSS) ® 6 7 v21.The raw data contained data on all ethnicities (N=21,264), however for the purposes of 8 9 10 this paper, data was selected for only white British, Pakistani, Indian and Bangladeshi 11 12 outcomes, statistics were conducted on live singleton infants only who were delivered after 13 14 24 weeks (reported as adjusted means) (N= 14,871). 15 For peer review only 16 17 18 19 Means, standard error, 95% confidence intervals (CI) were calculated for each ethnic group. 20 21 An ANCOVA was conducted to ascertain birthweight difference between ethnic groups and 22 23 to control for confounding variables (i.e. maternal age, smoking status, diabetes, gestation 24 25 age at delivery, parity and maternal height and BMI), with birthweight as the outcome 26 27 variable. Bonferonni post hoc analysis was used to determine where significant differences 28 29 30 were, if any. Pearson chi square test for association and adjusted standardised residual (ASR) 31 32 were used to test for associations between maternal ethnicity and gestation age at delivery. 33
34 However, to account for the effect of parity on gestation age at delivery, a filter variable was http://bmjopen.bmj.com/ 35 36 created to use only primapara (others were treated as missing), for the calculation of pre term 37 38 39 delivery. 40 41 42 Routinely collected secondary data was provided to the research team in a non identifiable 43 on October 1, 2021 by guest. Protected copyright. 44 form. Ethic approval was therefore not required from NRES but was obtained from the 45 46 University of Bedfordshire Research Ethics Committee (March 2014). Scrutiny from the 47 48 hospitals Information Governance Manager ensured adherence to patient confidentiality and 49 50 data protection before de identified routinely collected data was provided. 51 52 53 54 55 56 57 58 59 60 7
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 8 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Results: 4 5 Our results focus on mothers of white British, Indian, Pakistani and Bangladeshi ethnicity. 6 7 8 There were a total 15,211 births for the years 2008 2013, of which 14,871 were recorded in 9 10 CMiS as live singleton deliveries, which were delivered after 24 weeks of gestation. The 11 12 numbers of women recorded as being smokers, diagnosed with diabetes (type 1, type 2 and 13 14 gestational diabetes), maternal BMI at booking and gestational age at delivery are shown by 15 For peer review only 16 17 ethnic group (table 1), as these are recognised confounders to infant weight. There were 69 18 19 missing entries for diabetes (0.5%) and 29 cases of smoking data missing (0.2%) and 8 20 21 missing entries for BMI (0.05%). The cohort mean birthweight is 3214g. 22 23 24 25 An ANCOVA was used to determine the effect of maternal ethnicity on birthweight, and 26 27 28 adjusting confounders to birthweight. Birthweight is reported as unadjusted and adjusted 29 30 mean(s) and shown for each maternal ethnicity (table 2). The adjusted mean birthweight 31 32 results found Bangladeshi mothers had the lightest mean birthweights (3068.01g) compared 33
34 to white British mothers who delivered infants with a mean birthweight of 3375.66g, showing http://bmjopen.bmj.com/ 35 36 37 a difference of 307.65g g. The adjusted results showed a significant difference mean infant 38 39 birthweight by maternal ethnicity; F(3, 14781) = 310.23, p<.0005. The partial Eta squared 40 41 for maternal ethnicity was 2= .067. 42 on October 1, 2021 by guest. Protected copyright. 43 44 45 2 46 The covariates of BMI; F(1, 12384) = 242.43, p<.005, partial =.019), maternal smoking; 47 2 48 F(1, 12384)= 212.78, p<.005 partial =.017), maternal height (F(1, 12384) = 14.57, 49 50 p<.0005 partial 2 =.001) and parity F(1, 12384) = 33.07, p<.005, partial 2 =.003), had a 51 52 significant effect on birthweight, while the covariates of maternal diabetes and age was not 53 54 55 significant in this analysis. 56 57 58 59 60 8
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 9 9
899 37+ 6447 1908 4757 4757 (93.5) (93.5) (92.4) (93.6) (93.6) (93.9) (93.9) 14011
n(%) n(%)
weeks weeks 37 - Gestation Gestation 74 451 124 957 308 308 (6.5) (6.5) (7.6) (6.1) (6.4) (6.1) (6.1) 24
60 - 8 8 24 24 80 80 (2) (2) 294 294 182 182 40 (0.8) (0.8) (1.2) (1.2) (2.6) (2.6) (1.6) (1.6)
39.9 - 79 79 226 226 794 794 (15) (15) (8.1) (8.1) 1146 1146 2245 30 (11.1) (11.1) (16.6) (16.6) (15.6) (15.6)
29.9 - 262 262 546 BMI 1710 1710 3815 1297 1297 25 n(%) n(%) (26.9) (26.9) (26.8) (24.8) (24.8) (25.5) (25.6) (25.6)
24.9 - 424 424 757 (32) (32) 2518 2518 5323 1624 1624 19 (43.5) (43.5) (37.2) (36.5) (36.5) (35.5)
202 202 482 <18.5 1349 1349 3313 1280 1280 (20.7) (20.7) (23.7) (19.5) (19.5) (22.1) (25.2) (25.2)
54 14 68 253 117 117 (0.8) (0.8) (1.4) (3.4) (1.7) (2.3) (2.3) n(%) n(%) Diabetic
19 18 73 (2) (2) (0.9) (0.9) (1.4) (1.4) 1490 1600 n(%) n(%) (21.6) (21.6) (10.7) Smokers BMJ Open
9 9 97 97 38 38 13 13 (1) (1) >40 157 157 (1.4) (1.4) (0.7) (0.7) (1.3) (1.3) (0.4) (0.4) http://bmjopen.bmj.com/ 3
40 - 79 79 (6) (6) 599 599 378 378 123 123 36 (7.9) (7.9) (8.7) (8.7) (7.4) (7.4) (8.1) (8.1) 1179 1179
35 - 261 261 431 431 31 3278 3278 1487 1487 1099 1099 (21.9) (21.9) (21.5) (21.5) (21.6) (21.6) (26.8) (26.8) (21.2) (21.2)
n (%) (%) n 30 - 407 407 801 801 26 5077 5077 2010 2010 1859 1859 Maternal age Maternal on October 1, 2021 by guest. Protected copyright. (33.9) (33.9) (29.1) (29.1) (36.6) (36.6) (41.7) (41.7) (39.3) (39.3)
25 - 200 200 581 581 21 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml 3977 3977 1710 1710 1486 1486 (26.5) (26.5) (20.5) (20.5) (28.5) (28.5) (24.8) (24.8) (29.3) (29.3)
20
- 15 15 For peer review 91 only 217 217 16 (8.9) (8.9) (1.5) (1.5) (4.5) (4.5) (4.3) (4.3) 1329 1329 1006 1006 (14.6) (14.6)
971 live live (6.5) (6.5) 2013 6862 5025 n(%) n(%) (33.8) (33.8) (46.1) (46.1) (13.5) 14871 births births singleton singleton
Total Indian Maternal ethnicity ethnicity Pakistani Bangladeshi White British White
1: Table Cohort descriptive statisticslive for deliveriessingleton 2008 201
Page 9 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 BMJ Open Page 10 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 4 5 6 a 7 Table 2: unadjusted and adjusted mean birthweight for 2008 2013 by maternal ethnicity 95% Confidence Interval 8 Un- Maternal Std. Adjusted Std. 9 N adjusted a ethnicity Error mean Error Lower Bound Upper Bound mean 10 11 White British 5853 5.13 12 3352.51 3375.66 6.43 3363.07 3388.26 13 Indian 840 3045.53 4.64 3073.08 16.56 3040.62 3105.55 14 15 Pakistani For4013 peer3164.89 review4.71 3130.71 only 7.65 3115.72 3145.71 16 17 Bangladeshi 1689 3080.75 5.14 3068.01 11.7 3045.09 3090.93 18 19 a 20 Adjusted for maternal age, smoking status, diabetes, gestation age at delivery and maternal height, BMI and 21 parity 22 23 24 25 26 Bonferroni post hoc analysis revealed adjusted mean birthweight was statistically 27 28 significantly lower in Indian (M = 3073.08. SE = 17.83), Pakistani (M = 3130.71 SE = 29 30 10.74) and Bangladeshi (M = 3068.01 , SE = 13.62) compared with white British infants (M 31 32 =3375.66, SE = 6.43), a mean difference of 302.58g, 95% CI [255.53 349.62] p<.005, 33
34 (Indian), 307.65g 95% CI [271.72 343.59] p<.005 (Bangladeshi) and 244.95, 95% CI http://bmjopen.bmj.com/ 35 36 37 [217.84 272.06] (Pakistani) p<.005. Moreover, differences in adjusted mean birthweight 38 39 were found between Indian and Pakistani infants 57.63g, 95% CI [ 105.85—9.41] p<.01 and 40 41 Pakistani and Bangladeshi infants 62.7 g 95% CI [26.44 98.96] p<.005, but no significance 42 on October 1, 2021 by guest. Protected copyright. 43 was found between the adjusted mean birthweight of Indian and Bangladeshi infants. 44 45 46 47 48 Assessing only women delivering primapara infants (n= 6197), a chi square test for 49 50 association between maternal ethnicity and gestational age of delivery (24 36.9, and >37 51 52 weeks of gestation) found a significant association in Indian mothers delivering between 24 53 54 36.9 weeks of gestation (χ2 (3) = 9.9, p = .019) (table 3). 55 56 57 58 59 60 10
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 11 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Table 3: frequency counts, percentages and adjusted standardised residuals of delivery before and after 37 4 weeks of gestation shown by maternal ethnicity. 5 PTB 6 24-36.9 37+ Total 7 weeks weeks 2936 184 (5.9) 3120 8 Maternal ethnicity White British Count (94.1) 9 Adjusted Residual -1.1 1.1 10 Indian Count 56 (9) 564 (91) 620 11 Adjusted Residual 3.0 -3.0 12 Pakistani Count 101(5.7) 1665(94.3) 1766 13 Adjusted Residual -1.1 1.1 14 Bangladeshi Count 46 (6.7) 645(93.3) 691 15 For peerAdjusted review Residual only.5 -.5 16 Total Count 387 5810 6197 % within white and South 17 6.2% 93.8% 100.0% 18 Asian 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 11
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 12 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 4 Discussion: 5 The aim of this paper was to identify differences in birthweight and gestation age at delivery 6 7 between Indian, Pakistani and Bangladeshi and white British women. Differences between 8 9 10 the mean birthweights of Indian, Pakistani, Bangladeshi and white British infants were found, 11 12 in addition to an association between pre term delivery in primapara Indian mothers. 13 14 15 The results For showed that peer Indian infants review had the lightest unadjusted only mean birth weights, 16 17 followed by Bangladeshi, Pakistani and white British infants respectively. However, after 18 19 controlling for known confounders, Bangladeshi infants were found to have the lightest mean 20 21 22 birthweight. Not unexpectedly, maternal smoking, maternal height, BMI and parity showed a 23 24 significant independent contribution to the outcome of infant birthweight. Furthermore, an 25 26 association was found between primipara Indian mothers and pre term delivery, within this 27 28 cohort. 29 30 31 Leon and Moser[14] also found Bangladeshi infants were the lightest, compared with Indian, 32 33 Pakistani or white British infants. On the other hand, the MCS[12] calculated birthweight
34 http://bmjopen.bmj.com/ 35 36 gestation age at delivery using self reported data and found that the unadjusted mean 37 38 birthweight was lightest in Indian infants, followed by Bangladeshi, Pakistani and white 39 40 British respectively. Furthermore, the adjusted mean calculations showed a number of 41 42 different findings according to the variables controlled; maternal and infant factors (i.e. on October 1, 2021 by guest. Protected copyright. 43 44 45 gestation age, parity, maternal height and weight and antenatal complications) found 46 47 Pakistani infants were lightest, whereas when controlling for behavioural factors (i.e. 48 49 antenatal care, smoking and drinking) and socioeconomic factors (i.e. household income, 50 51 education status, occupation status, single parentage, and housing tenure) showed Indian 52 53 54 infants were lightest. Margetts et al[4], results also showed that infants delivered to mothers 55 56 born in India had lighter infants, while Pakistani born mothers had heavier infants, however, 57 58 59 60 12
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 13 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 their results were only adjusted for generation status, therefore the mean weight reported in 4 5 the paper is unadjusted. 6 7 8 Taken together, this is suggestive that birthweight might be sensitive to different 9 10 combinations of mediators, which may vary according to maternal ethnicity, an important 11 12 13 point for specific antenatal interventions[40]. Moreover, a further explanation of the results 14 15 found in thisFor study is that peer that birthweight review is sensitive to environmental only influences and the 16 17 national level figures used in Leon and Moser’s analysis will average out regional variations, 18 19 as evidenced in the current paper, which focuses on mean birthweights specifically in 20 21 22 Luton[14,41]. Furthermore, these results fail to support the current explanation that South 23 24 Asian infants are lighter as a consequence of their parents being of a smaller 25 26 stature[19,46,47], since BMI at booking and maternal height was controlled and adjusted 27 28 mean birthweight was still found to be significantly lighter in all South Asian ethnicities, 29 30 compared with WB. 31 32 33 While Patel and colleagues used a large South Asian sample size (n=16 192) found an
34 http://bmjopen.bmj.com/ 35 36 increased OR for South Asian mothers having a pre term birth in their study[18], they 37 38 aggregated Pakistani, Bangladeshi and Indian mothers, which obscured any sub group trends. 39 40 However, our study assessed pre term delivery in primapara Pakistani, Bangladeshi Indian 41 42 and white British mothers and found a significant association between pre term delivery and on October 1, 2021 by guest. Protected copyright. 43 44 45 Indian mothers; although it is recognised that socioeconomic factors were not controlled in 46 47 this cohort. 48 49 50 The MCS also showed that Indian mothers had a higher rate of preterm birth compared to 51 52 Pakistani and Bangladeshi mothers, however, similar to the present study, the analyses was 53 54 restricted to a binary outcome of births 24 37 weeks of gestation and after 37 weeks of 55 56 57 gestation (hence excluding pre viable births). Therefore, this results in the loss of some 58 59 60 13
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 14 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 information; exclusion of pre viable births (i.e. <24 weeks of gestation) means that it is 4 5 impossible to compare the frequency of early pregnancy loss by maternal ethnicity[12]. 6 7 Higher rates of early loss may well be evident in Pakistani mothers, due to a higher 8 9 10 prevalence of congenital anomalies, some of which may be lethal, but this as yet needs to be 11 12 elucidated[42]. 13 14 15 Taken togetherFor these resultspeer highlight review a number of key findings.only Firstly that there are 16 17 important differences between Pakistani, Bangladeshi and Indian infant birthweights, 18 19 whereby treating them in research terms as a homogenous group categorised as ‘South Asian’ 20 21 22 obscures distal determinants. Researchers should move away from using the category of 23 24 ‘South Asian’ and be more specific about ethnicity when reporting populations under study. 25 26 Secondly, when comparing the findings with previous studies [4,12,18,43], this study shows 27 28 that the confounding variables controlled for also influences the results of which maternal 29 30 ethnicity has the lightest mean birthweight; suggestive that a closer examination of maternal 31 32 33 and behavioural mediators is warranted. It is possible that contributors for LBW in one
34 http://bmjopen.bmj.com/ 35 population are less pronounced in another and these factors need to be better understood. 36 37 Furthermore, while there are known trends such as LBW in South Asian mothers[27,28], 38 39 there are also clear ethnic and regional variations, suggestive of mediating social and 40 41 42 environmental factors, which warrant further investigation. 43 on October 1, 2021 by guest. Protected copyright. 44 45 This study has a number of strengths; the large sample sizes of the Indian, Pakistani and 46 47 Bangladeshi mothers, compared to the MCS[12], whereby the authors over sampled from 48 49 BAME populations, actually had smaller sample sizes from Indian (n = 433), Pakistani (n= 50 51 687) and Bangladeshi mothers (n= 215) than the present study, whose subgroup sample size 52 53 54 is substantially larger, providing more generalisable results. In addition, it accesses 5 years’ 55 56 worth of data, which provides a more reliable picture and addresses any cohort anomalies that 57 58 may occur in shorter duration datasets. 59 60 14
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 15 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 This study is not without limitations. Hypertension in pregnancy is known to contribute to 4 5 growth restriction, placental problems and increase maternal mortality risk. However, in this 6 7 cohort, the data reported only 12 cases; therefore while this was excluded from analysis it 8 9 10 may have had a clinical impact which not accounted for. Furthermore, while the sample sizes 11 12 for Indian, Pakistani and Bangladeshi mothers was larger than the MCS, our Indian sample 13 14 size was still relatively small. In addition, there were no socioeconomic measures available to 15 For peer review only 16 the research team to allow controlling of socioeconomic factors known to mediate pre term 17 18 19 birth in this study. It would be beneficial for future research to investigate further trends in 20 21 pre term birth and Pakistani, Bangladeshi and Indian infants, while controlling for 22 23 socioeconomic factors, especially as there are known differences in the socioeconomic status 24 25 between Indian, Pakistani and Bangladeshi ethnic groups in England[44]. 26 27 28 In conclusion this study presents important differences in mean birthweights between Indian, 29 30 Pakistani and Bangladeshi infants. Furthermore, an association between primapara Indian 31 32 33 mothers and pre term birth was found. LBW and PTB both contribute significantly to
34 http://bmjopen.bmj.com/ 35 mortality and morbidity outcomes, therefore understanding the reasons for this disparity is 36 37 essential for levelling up service provision and policy planning[20,21,45,46]. 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 15
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 16 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Acknowledgments 4 We would like to thank Martina McIntyre for extracting the de identified data from CMiS 5 6 and Tessa Pollard for her helpful comments on earlier drafts of this manuscript. 7 8 Competing Interests 9 10 The authors declare that there are no competing interests. 11 12 Contributions 13 14 RG and NA conceived the study; MG assisted in identification of data, RG and AG 15 conducted theFor statistical analyses,peer RG, NA,review GR, AG, and MG contributedonly to earlier drafts of 16 the manuscript and all authors agreed the final version. 17 18 19 Funding 20 The Steel Trust has provided funding to the University of Bedfordshire for RG to undertake 21 research at Institute for Health Research, University of Bedfordshire, under the direction of 22 NA and GR. The funders have no involvement in the research or publication. 23 24 Data sharing statement 25 26
27 No additional data are available 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 16
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 17 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 References 4 1 Messer J. An analysis of the socio demographic characteristics of sole registered births 5 6 and infant deaths. Health Stat Q 2011;:79–107. doi:10.1057/hsq.2011.9 7 2 Institute of Health Economics. Determinants and Prevention of Low Birth Weight : A 8 Synopsis of the Evidence. Alberta, Canada: 2008. 9 10 3 De Farias Aragão VM, Barbieri MA, Moura Da Silva AA, et al. Risk factors for 11 intrauterine growth restriction: a comparison between two Brazilian cities. Pediatr Res 12 2005;57:674–9. doi:10.1203/01.PDR.0000156504.29809.26 13 14 4 Margetts BM, Yusof SM, Dallal Z Al, et al. Persistence of lower birth weight in 15 secondFor generation peerSouth Asian babies review born in the UK. J onlyEpidemiol Community Health 16 2002;56:684–7. 17 18 5 Joshi K, Sochaliya KM, Shrivastav A V, et al. A hospital based study on the 19 prevalence of low birth weight in newborn babies and its relation to maternal health 20 factors. Int J Res Med 2014;3:4–8. 21 22 6 World Health Organisation. Promoting Optimal Fetal Development: Report of a 23 Technical Consultation. Geneva: 2006. 24 http://www.who.int/nutrition/publications/fetal_dev_report_EN.pdf 25 26 7 Kramer MS. Determinants of low birth weight : methodological assessment and meta 27 analysis. Bull World Health Organ 1987;65:663– 28 737.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2491072/pdf/bullwho00076 29 0086.pdf 30 31 8 Escobar GJ, Littenberg B, Petitti DB. Outcome among surviving very low birthweight 32 infants : a meta analysis. Arch Dis Child 1991;66:204–11. 33 9 Blencowe H, Cousens S, Chou D, et al. Born too soon: the global epidemiology of 15
34 http://bmjopen.bmj.com/ 35 million preterm births. Reprod Health 2013;10 Suppl 1:S2. doi:10.1186/1742 4755 36 10 S1 S2 37 10 Lausman A, Kingdom J. Intrauterine Growth Restriction : Screening , Diagnosis and 38 Management. J Obs Gynaecol Can 2013;35:741–8.http://sogc.org/wp 39 40 content/uploads/2013/08/August2013 CPG295 ENG Revised.pdf 41 11 Perinatal Institute for Maternal and Child Health. Intrauterine growth restriction, 42 stillbirths and prevention. Prevalence of IUGR. 2011. on October 1, 2021 by guest. Protected copyright. 43 http://www.pi.nhs.uk/pnm/clinicaloutcomereviews/index.htm 44 45 12 Kelly Y, Panico L, Bartley M, et al. Why does birthweight vary among ethnic groups 46 in the UK? Findings from the Millennium Cohort Study. J Public Health (Oxf) 47 2009;31:131–7. doi:10.1093/pubmed/fdn057 48 49 13 Jayaweera H, Joshi H, MacFarlane A, et al. Pregnancy and childbirth. In: Dex S, Joshi 50 H, eds. Children of the 21st Century. Bristol: : The Policy Press 2005. 109–33. 51 52 14 Leon DA, Moser KA. Low birth weight persists in South Asian babies born in England 53 and Wales regardless of maternal country of birth. Slow pace of acculturation, 54 physiological constraint or both? Analysis of routine data. J Epidemiol Community 55 Health 2012;66:544–51. doi:10.1136/jech.2010.112516 56 57 15 Oldroyd J. Low Birth Weight in South Asian babies in Britain: Time to reduce the 58 inequalities. Fuckusihima J Med Sci 2005;51:1–10. 59 60 17
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 18 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 16 West J, Lawlor D a., Fairley L, et al. UK born Pakistani origin infants are relatively 4 more adipose than white British infants: findings from 8704 mother offspring pairs in 5 the Born in Bradford prospective birth cohort. J Epidemiol Community Heal 6 2013;67:544–51. doi:10.1136/jech 2012 201891 7 8 17 Dhawan S. Birth weights of infants of first generation Asian women in Britain 9 compared with second generation Asian women. BMJ 1995;311:86– 10 8.http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2550148&tool=pmcentre 11 z&rendertype=abstract 12 13 18 Patel RR, Steer P, Doyle P, et al. Does gestation vary by ethnic group ? A London 14 based study over 122 , 000 pregnancies with spontaneous onset of labour. Int J 15 EpidemiolFor 2003; 33peer:107–13. doi:10.1093/ije/dyg238 review only 16 17 19 Bansal N, Ayoola OO, Gemmell I, et al. Effects of early growth on blood pressure of 18 infants of British European and South Asian origin at one year of age: the Manchester 19 children growth and vascular health study. J Hypertens 2008;26:412–8. 20 doi:10.1097/HJH.0b013e3282f3168e 21 22 20 Hollowell J, Kurinczuk JJ, Brocklehurst P, et al. Social and ethnic inequalities in 23 infant mortality: a perspective from the United kingdom. Semin Perinatol 24 2011;35:240–4. doi:10.1053/j.semperi.2011.02.021 25 26 21 Zeitlin J, Szamotulska K, Drewniak N, et al. Preterm birth time trends in Europe: a 27 study of 19 countries. BJOG 2013;120:1356–65. doi:10.1111/1471 0528.12281 28 29 22 The National Institute for Health and Care Excellence. Maternal and Child Nutrition. 30 2010. http://www.nice.org.uk/guidance/ph11/resources/guidance maternal and child 31 nutrition pdf 32 23 Bansal N, Chalmers JWT, Fischbacher CM, et al. Ethnicity and first birth: age, 33 smoking, delivery, gestation, weight and feeding: Scottish health and ethnicity linkage
34 http://bmjopen.bmj.com/ 35 study. Eur J Public Health 2014;2008:1–6. doi:10.1093/eurpub/cku059 36 24 Han Z, Mulla S, Beyene J, et al. Maternal underweight and the risk of preterm birth 37 and low birth weight : a systematic review and meta analyses. Int J Epidemiol 38 39 2011;40:65–101. doi:10.1093/ije/dyq195 40 25 Loret de Mola C, Araújo de França GV, Quevedo LDA, et al. Low birth weight, 41 preterm birth and small for gestational age association with adult depression: 42 43 systematic review and meta analysis. Br J Psychiatry 2014;205:340–7. on October 1, 2021 by guest. Protected copyright. 44 doi:10.1192/bjp.bp.113.139014 45 26 Office for National Statistics. Statistical Bulletin Births in England and Wales by 46 Parents’ Country of Birth: 2013. 2014. 47 48 27 Harding S, Rosato MG, Cruickshank JK. Lack of change in birthweights of infants by 49 generational status among Indian, Pakistani, Bangladeshi, Black Caribbean, and Black 50 African mothers in a British cohort study. Int J Epidemiol 2004;33:1279–85. 51 doi:10.1093/ije/dyh186 52 53 28 Moser K, Stanfield KM, Leon D a. Birthweight and gestational age by ethnic group, 54 England and Wales 2005: introducing new data on births. Health Stat Q 2008;:22–31, 55 34–55.http://www.ncbi.nlm.nih.gov/pubmed/18810886 56 57 29 Office for National Statistics. Statistical Bulletin Childhood, Infant and Perinatal 58 59 60 18
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 19 of 22 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Mortality in England and Wales, 2012. 2012. 4 http://www.ons.gov.uk/ons/rel/vsob1/child mortality statistics childhood infant and 5 perinatal/2012/ 6 7 30 Kent ST, McClure L a, Zaitchik BF, et al. Area level risk factors for adverse birth 8 outcomes: trends in urban and rural settings. BMC Pregnancy Childbirth 2013;13:129. 9 doi:10.1186/1471 2393 13 129 10 11 31 Yadav H, Lee N. Maternal factors in predicting low birth weight babies. Med J 12 Malaysia 2013;68:44–7. 13 14 32 Garcia RL, Ali N, Papadopoulos C, et al. Specific antenatal interventions for Black, 15 AsianFor and Minority peer Ethnic (BAME) review pregnant women at onlyhigh risk of poor birth 16 outcomes in the United Kingdom: A scoping review. BMC Pregnancy Childbirth 17 Published Online First: 2015.http://www.biomedcentral.com/1471 2393/15/226 18 19 33 Kim D, Saada A. The social determinants of infant mortality and birth outcomes in 20 western developed nations: A cross country systematic review. Int J Environ Res 21 Public Health 2013;10:2296–335. doi:10.3390/ijerph10062296 22 34 Cresswell J a, Yu G, Hatherall B, et al. Predictors of the timing of initiation of 23 24 antenatal care in an ethnically diverse urban cohort in the UK. BMC Pregnancy 25 Childbirth 26 2013;13:103.http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3652742&too 27 l=pmcentrez&rendertype=abstract 28 29 35 Ravelli ACJ, Tromp M, Eskes M, et al. Ethnic differences in stillbirth and early 30 neonatal mortality in The Netherlands. J Epidemiol Community Health 2011;65:696– 31 701. doi:10.1136/jech.2009.095406 32 36 Freemantle J, Wood C, Griffin C, et al. What factors predict differences in infant and 33 perinatal mortality in primary care trusts in England? A prognostic model. BMJ
34 http://bmjopen.bmj.com/ 35 2009;339:b2892. doi:10.1136/bmj.b2892 36 37 Silverwood RJ, Pierce M, Hardy R, et al. Low birth weight, later renal function, and 37 the roles of adulthood blood pressure, diabetes, and obesity in a British birth cohort. 38 39 Kidney Int 2013;84:1262–70. doi:10.1038/ki.2013.223 40 38 Department of Health. Data standards: Ethnic category. 2008. 41 http://webarchive.nationalarchives.gov.uk/+/http://www.isb.nhs.uk/documents/dscn/ds 42 43 cn2008/dataset/112008.pdf on October 1, 2021 by guest. Protected copyright. 44 39 Economic and Social Data Service. Ethnicity : Introductory User Guide. 2012. 45 http://www.esds.ac.uk/government/docs/ethnicityintro.pdf 46 47 40 Garcia RL, Ali N, Papadopoulos C, et al. Specific antenatal interventions for Black, 48 Asian and Minority Ethnic (BAME) pregnant women at high risk of poor birth 49 outcomes in the United Kingdom: A scoping review. BMC Pregnancy Childbirth 50 Published Online First: 2015.http://www.biomedcentral.com/1471 2393/15/226 51 52 41 Enkin M, Chalmers I. Effectiveness and satisfaction in antenatal care. In: Enkin U, 53 Chalmers I, eds. Antenatal Care. London: : Heinemann Medical. 1982. 266–90. 54 55 42 Kurinczuk JJ, Hollowell J, Boyd PA, et al. The contribution of congenital anomalies to 56 infant mortality. 2010. 57 58 43 Leon DA, Moser KA. Low birth weight persists in South Asian babies born in England 59 60 19
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 20 of 22 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 and Wales regardless of maternal country of birth. Slow pace of acculturation, 4 physiological constraint or both? Analysis of routine data. J Epidemiol Community 5 Heal 2012;66:544–51. doi:10.1136/jech.2010.112516 6 7 44 Platt L. Inequality within ethnic groups. 2011. 8 http://www.jrf.org.uk/sites/files/jrf/inequality ethnicity poverty full.pdf 9 10 45 Whitehead M, Dahlgren G. Concepts and principles for tackling social inequities in 11 health : Levelling up Part 1. World Heal Organ 2007;:1– 12 45.http://www.euro.who.int/__data/assets/pdf_file/0010/74737/E89383.pdf 13 14 46 Dahlgren G, Whitehead M. European strategies for tackling social inequities in 15 health:For Levelling uppeer part 2. World review Health Organisation 2007.only 16 http://www.euro.who.int/__data/assets/pdf_file/0018/103824/E89384.pdf 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 20
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Differences in the pregnancy gestation period and mean birthweights in infants born to Indian, Pakistani, Bangladeshi and white British mothers in Luton: A retrospective analysis of routinely collected data.
For peer review only Journal: BMJ Open
Manuscript ID bmjopen-2017-017139.R1
Article Type: Research
Date Submitted by the Author: 07-Jun-2017
Complete List of Authors: Garcia, Rebecca; University of Bedfordshire, Institute for Health Research Ali, Nasreen; University of Bedfordshire Faculty of Health and Social Sciences, Institute for Health Research Guppy, Andy; University of Bedfordshire, Department of Psychology Griffiths, Malcolm; 3Luton &Dunstable University Hospital NHS Foundation Trust, Obsetrics Randhawa, Gurch; University of Bedfordshire, Institute for Health Research
Primary Subject Health services research Heading:
Secondary Subject Heading: Obstetrics and gynaecology, Public health, Health services research http://bmjopen.bmj.com/ Keywords: Low birthweight, Pakistani, South Asian, Bangladeshi, Indian
on October 1, 2021 by guest. Protected copyright.
For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 1 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Differences in the pregnancy gestation period and mean birthweights in 4 5 infants born to Indian, Pakistani, Bangladeshi and white British mothers in 6 Luton: A retrospective analysis of routinely collected data. 7 8 Rebecca Garcia1, #, Nasreen Ali1, Andy Guppy 2, Malcolm Griffiths3, Gurch Randhawa1 9 10 11 12 1 The Institute For Health Research, 2 The Institute for Applied Social Sciences, University of 13 Bedfordshire, Putteridge Bury, Hitchin Road, Luton, Bedfordshire, LU2 8LE. 14 15 3 Luton &DunstableFor University peer Hospital NHS review Foundation Trust, Lewsey only Rd, Luton, LU4 0DZ 16 17 #corresponding author 18 19 Telephone 01582 743744 20 21 22 23 Email addresses: 24 25 RG: [email protected] 26 27 NA: [email protected] 28 AG: [email protected] 29 30 MG: [email protected] 31 GR: [email protected] 32 33
34 http://bmjopen.bmj.com/ 35 36 37 Keywords: low birthweight, gestation, south Asian, Pakistani, Indian Bangladeshi 38 39 40 41 Word count 42 on October 1, 2021 by guest. Protected copyright. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 2 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Objective 4 5 To compare mean birthweights and gestational age at delivery of infants born to Indian, 6 Pakistani, Bangladeshi and white British mothers in Luton, UK. 7 8 Design 9 10 11 Retrospective analysis using routinely recorded secondary data in Ciconia Maternity 12 information System (CMiS), between 2008 and 2013. 13 14 15 Setting: For peer review only 16 17 Luton, UK 18 19 Participants 20 21 Mothers whose ethnicity was recorded as white British, Bangladeshi, Pakistani or Indian and 22 living in Luton, aged over 16, who had a live singleton birth over 24 weeks of gestation were 23 24 included in the analysis (N= 14,871). 25 26 Outcome measures 27 28 Primary outcome measures were mean birthweight and gestational age at delivery 29 30 Results 31 32 After controlling for maternal age, smoking, diabetes, gestation age, parity and maternal 33 height and BMI at booking, a significant difference in infants mean birthweight was found
34 between white British and Indian, Pakistani and Bangladeshi infants, F(3, 12287) = 300.32, http://bmjopen.bmj.com/ 35 p<.0005. The partial Eta squared for maternal ethnicity was 2= .067. The adjusted mean 36 birthweight for white British infants was found to be 3377.89g (95% CI 3365.34 3390.44), 37 38 Indian infants 3033.09g (95% CI 3038.63 3103.55), Pakistani infants 3129.49g(95% CI 39 3114.5 3144.48) and Bangladeshi infants 3064.21g (95% CI 3041.36 3087.06. There was a 40 significant association in pre term delivery found in primapara Indian mothers, compared 41 with Indian mothers (Wald = 8.192, df 1, p=.004). 42 Conclusions 43 on October 1, 2021 by guest. Protected copyright. 44 Results show important differences in adjusted mean birthweight between Indian, Pakistani, 45 Bangladeshi and white British women. Moreover, an association was found between 46 primapara Indian mothers and pre term delivery, when compared with Pakistani, Bangladeshi 47 and white British women. 48 49 50 51 52 53 54 55 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 3 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Strengths and Limitations of the study 4 5 • This study uses retrospective routinely collected data over six years providing a large 6 sample size, (N=14,871), providing more generalisable results. 7 8 • This paper adds to the sparse existing evidence which examines heterogeneity in 9 10 birthweight and gestation age at delivery between women from South Asia in the UK. 11 12 • This study was unable to accurately identify socio economic measures and 13 subsequently control for, and analyse these, understanding that socio economic 14 15 factorsFor may have peercontributed to thereview study results. only 16 17 18 19 Introduction 20 Low birthweight (LBW) is a significant contributory factor for increased risk of infant 21 22 mortality and morbidity[1], and has health consequences extending into adulthood[2].It is 23 24 also a recognised proxy for maternal health[3,4]. LBW is defined as birthweight of less than 25 26 27 2500g at birth[5,6]. The rather arbitrary figure of 2500g was determined by the World Health 28 29 Organisation, as birthweight less than this shows a substantially increased mortality rate[7]. 30 31 Birthweight of 1500 g is classified as very low birthweight (VLBW) and has an exponentially 32 33 higher mortality rate[8]. V/LBW may be a consequence of a number of mediating factors
34 http://bmjopen.bmj.com/ 35 36 including pre term birth (PTB)[9], small for gestational age (SGA)[6,10] and intrauterine 37 38 growth restriction (IUGR), whereby the normal development of the fetus is hampered[11]. 39 40 41 42
Existing evidence shows that South Asian women typically give birth to infants of lower on October 1, 2021 by guest. Protected copyright. 43 44 birthweights than white British women[12,13] with babies on average being 230 350g 45 46 47 lighter[14–16]. Typically, statistics in the UK uses aggregated data from Indian, Pakistani 48 49 and Bangladeshi infants/mothers, as ‘South Asian’[4,17–19]; obscuring nuances between 50 51 each ethnic group[20], or have been reported as ‘South Asian’ when only one specific ethnic 52 53 group is reported (e.g. Pakistani) [16,19]. Research documents a host of maternal, infant and 54 55 56 social factors contributing to LBW, for example; gestational age at delivery [21] poor 57 58 maternal nutrition[22], smoking[23], maternal underweight[24], socioeconomic status[5], and 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 4 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 maternal depression[25]. Studies have also assessed differences in maternal country of birth 4 5 on birthweights[14,26], and between generations[4,14,27]. 6 7 8 9 10 Lighter birthweight infants in South Asian infants are well documented[12,14,19]. Margetts 11 12 and colleagues[4], defined South Asian mothers originating from the Indian sub continent 13 14 using either maternal place of birth e.g. India, Pakistan or Bangladesh (as first generation) or 15 For peer review only 16 UK born (as second generation). They reported differences in the mean birthweights of first 17 18 19 generation Indian (3077g), Bangladeshi (3161g) and Pakistani (3235g) infants. The same 20 21 trend was observed in the Millennium Cohort Study (MCS) whereby Indian mothers have the 22 23 lightest infants and Pakistani mothers had the heaviest[12]. Conversely, Leon and 24 25 Moser[14]found Bangladeshi infants were the lightest, while consistent with the other 26 27 studies; Pakistani infants were heaviest among the infants born to South Asian mothers. 28 29 30 31 32 Margetts et al[4] restricted their analyses to births after thirty seven weeks, which eliminated 33
34 trends accounted for by gestational age, in addition to aggregating maternal ethnicity to http://bmjopen.bmj.com/ 35 36 assess for differences between maternal generations (i.e. born in the Indian Subcontinent 37 38 39 classified as first generation or UK classified as second generation). While the MCS showed 40 41 that Pakistani mothers had a lower rate of pre term delivery, the study showed that Indian 42 43 mothers had a higher rate[12]. Moreover, national figures for 2012 showed Bangladeshi on October 1, 2021 by guest. Protected copyright. 44 45 mothers had higher rate of infant mortality, conversely, Pakistani and Indian mothers had 46 47 higher preterm delivery rates[28] while Pakistani mothers had a higher preterm delivery 48 49 50 mortality rate, when compared to British women[29]. Together this demonstrates discreet 51 52 differences between birth patterns of women of South Asian ethnicity in the UK. 53 54 55 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 5 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 LBW is a complex research area that has been hampered by inconsistent research methods 4 5 and outcome measures such as mean birthweight[4,14], or weight frequencies [3,30,31], or 6 7 aggregated ethnicities[4], thereby making comparison between studies difficult. It is 8 9 10 important to tease out the nuances of low birthweight trends between Indian, Pakistani and 11 12 Bangladeshi mothers in order to uncover modifiable factors before specific tailored 13 14 interventions are developed[32] and by identifying differences in birthweight and gestational 15 For peer review only 16 age at delivery between Indian, Pakistani and Bangladeshi and white British women in Luton, 17 18 19 England this paper makes a contribution to this research area. 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 6 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Methods 4 5 Routinely collected retrospective data from Ciconia Maternity information System (CMiS) 6 7 from the Luton and Dunstable University Hospital was used. The CMiS database is a clinical 8 9 information system used in some maternity departments in the UK to record all births (i.e. 10 11 hospital and home). Purposive sampling of women aged over 16 and all birth outcomes (i.e. 12 13 14 live and perinatal mortality), who gave birth between January 2008 and December 2013, 15 For peer review only 16 residing in specified postcode areas were included. 17 18 19 Variables: 20 21 Outcome variables of mean birthweight and pre term gestation age were used. Known 22 23 confounders were maternal age (16 20, 21 25, 26 30, 31 35, 36 40, >40), smoking (binary 24 25 variable smoker/non smoker), parity, diabetes (binary variable), gestation age (binary 26 27 28 variable <24 weeks of gestation excluded, 24 37 weeks of gestation and after 37 weeks of 29 30 gestation) and maternal height and BMI at booking were included and controlled [31,33–36]. 31 32 Maternal hypertension is associated with increased risks of adversity in pregnancy for mother 33
34 and fetus, including placental problems and intrauterine growth restriction[37]. However, the http://bmjopen.bmj.com/ 35 36 37 CMiS data (for white British, Indian, Pakistani and Bangladeshi records) only had 12 data 38 39 entries recorded for maternal hypertension; the reasons for the lack of data are unknown and 40 41 therefore to avoid error, the variable was excluded from this analysis. 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 Recording ethnicity in the NHS is a mandatory requirement and staff are required to ask 47 48 49 women for their self ascribed ethnicity, according to the 2001 census categories[38] Ethnicity 50 51 is a self defined construct, which incorporates culture, religion, shared language and 52 53 ancestry[39]. Consequently, within this study, maternal country of birth, length of residency 54 55 or generational status was not ascertained, but the broader self classification of ethnicity as 56 57 recorded in the NHS are used for analysis. Cases with missing data were excluded. 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 7 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Statistical analysis: 4 5 Analyses were conducted using IBM Statistics Package for the Social Sciences (SPSS) ® 6 7 v21.The raw data contained data on all ethnicities (N=21,264), however for the purposes of 8 9 10 this paper, data was selected for only white British, Pakistani, Indian and Bangladeshi 11 12 outcomes, statistics were conducted on live singleton infants only who were delivered after 13 14 24 weeks (reported as adjusted means) (N= 14,871). 15 For peer review only 16 17 18 19 Frequency counts and percentages were calculated. ANOVA was used to determine whether 20 21 there were any significant differences in birthweight between the four ethnic groups and each 22 23 confounder variable (i.e. maternal age, smoking status, diabetes, gestation age at delivery, 24 25 parity and maternal height and BMI). Means, standard error, 95% confidence intervals (CI) 26 27 were calculated for each ethnic group. An ANCOVA was conducted to ascertain birthweight 28 29 30 difference between ethnic groups and to control for confounding variables with birthweight 31 32 as the outcome variable. Bonferonni post hoc analysis was used to determine where 33
34 significant differences were, if any. Pearson chi square test for association and adjusted http://bmjopen.bmj.com/ 35 36 standardised residual (ASR) were used to test for associations between maternal ethnicity and 37 38 39 gestation age at delivery. However, to account for the effect of parity on gestation age at 40 41 delivery, a filter variable was created to use only primapara (others were treated as missing), 42 43 for the calculation of pre term delivery. Multiple regressions were used to determine variance on October 1, 2021 by guest. Protected copyright. 44 45 explained of smoking on birthweight and logistic regression was used to determine whether 46 47 ethnicity increased the odds ratio for PTB. 48 49 50 Routinely collected secondary data was provided to the research team in a non identifiable 51 52 53 form. Ethic approval was therefore not required from NRES but was obtained from the 54 55 University of Bedfordshire Research Ethics Committee (March 2014). Scrutiny from the 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 8 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 hospitals Information Governance Manager ensured adherence to patient confidentiality and 4 5 data protection before de identified routinely collected data was provided. 6 7 8 9 10 11 12 13 14 15 For peer review only 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 9 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Results: 4 5 Our results focus on mothers of white British, Indian, Pakistani and Bangladeshi ethnicity. 6 7 8 There were a total 15,211 births for the years 2008 2013, of which 14,871 were recorded in 9 10 CMiS as live singleton deliveries, which were delivered after 24 weeks of gestation. The 11 12 frequencies and percentages of women recorded as being smokers, diagnosed with diabetes 13 14 (type 1, type 2 and gestational diabetes), maternal BMI at booking and gestational age at 15 For peer review only 16 17 delivery are shown by ethnic group (table 1), as recognised confounders to infant weight. A 18 19 series of ANOVAS found significant differences between birthweight and each ethnicity for 20 21 each confounding variable and these shown in table 1. There were 69 missing entries for 22 23 diabetes (0.5%) and 29 cases of smoking data missing (0.2%) and 8 missing entries for BMI 24 25 (0.05%). The cohort mean birthweight is 3214g. 26 27 28 29 30 31 32 An ANCOVA was used to determine the effect of maternal ethnicity on birthweight, and 33
34 adjusting confounders to birthweight. Birthweight is reported as unadjusted and adjusted http://bmjopen.bmj.com/ 35 36 37 mean(s) and shown for each maternal ethnicity (table 2). The adjusted mean birthweight 38 39 results found Bangladeshi mothers had the lightest mean birthweights (3068.01g) compared 40 41 to white British mothers who delivered infants with a mean birthweight of 3375.66g, showing 42 on October 1, 2021 by guest. Protected copyright. 43 a difference of 307.65g. The adjusted results showed a significant difference mean infant 44 45 birthweight by maternal ethnicity; F(3, 14781) = 310.23, p<.0005. The partial Eta squared 46 47 2 48 for maternal ethnicity was = .067. 49 50 51 52 The covariates of BMI; F(1, 12384) = 242.43, p<.005, partial 2 =.019), maternal smoking; 53 54 F(1, 12384)= 212.78, p<.005 partial 2 =.017), maternal height (F(1, 12384) = 14.57, 55 56 2 2 57 p<.0005 partial =.001) and parity F(1, 12384) = 33.07, p<.005, partial =.003), had a 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 10 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 significant effect on birthweight, while the covariates of maternal diabetes and age was not 4 5 significant in this analysis. 6 7 8 9 10 Table 1: Cohort frequencies and percentages of live singleton deliveries, age, smokers, 11 diabetes, BMI and gestation for 2008 2013 12 White Indian Pakistani Bangladeshi Total 13 British 14 Live 6862 1710 5025 2013 14871 15 singletons For peer review only 16 N(%) (46.1) (24.8) 33.8) (13.5) 17 18 P <.001 .370 <.001 <.001 19 20 Maternal 16 20 1006 15 217 91 1329 21 age (14.6) (1.5) (4.3) (4.5) (8.9) 22 21 25 1710 200 1486 581 3977 N(%) (24.8) (20.5) (29.3) (28.5) (26.5) 23 26 30 2010 407 1859 801 5077 24 (29.1) (41.7) (36.6) (39.3) (33.9) 25 26 31 35 1487 261 1099 431 3278 27 (21.5) (26.8) (21.6 (21.2) (21.9) 36 40 599 79 378 123 1179 28 (8.7) (8.1) (7.4) (6) (7.9) 29 40+ 97 13 38 9 157 30 (1.4) (1.3) (0.7) (0.4) (1) 31 p <.001 <.001 <.001 <.001 32 Smokers 1490 19 73 18 1600 33 (21.6) (2) (1.4) (0.9) (10.7)
34 N(%) http://bmjopen.bmj.com/ 35 36 p .001 .002 .031 .016 37 38 Diabetic 54 14 117 18 253 39 (0.8) (1.4) (2.3) (0.9) (1.7) 40 p .11 .08 .54 .39 41 BMI 19 24.9 2518 424 1624 757 5323 42 (36.5) (43.5) (32) (37.2) (35.5) on October 1, 2021 by guest. Protected copyright. 43 N(%) 44 25 29.5 1710 262 1297 546 3815 45 (24.6 (26.9) (25.6) (26.8) (25.5) 30 39.9 1146 79 794 226 2245 46 (16.6) (8.1) (15.6) (11.1) (15) 47 40 50 182 8 80 24 294 48 (2.6) (0.8) (1.6) (1.2) (2) 49 p <.001 .07 <.001 <.001 50 51 Gestation 24 37 451 74 308 124 957 (in weeks) (6.5) (7.6) (6.1) (6.1) (6.4) 52 37+ 6447 899 4757 1908 14011 53 N(%) (93.5) (92.4) (93.9) (93.6) (93.6) 54 55 p <.001 <.001 <.001 <.001 56 57 58 59 60 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 11 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 4 5 Table 2: unadjusted and adjusteda mean birthweight for 2008 2013 by maternal ethnicity 6 95% Confidence Interval Un- 7 Maternal Std. Adjusted Std. N adjusted ethnicity Error meana Error Lower Bound Upper Bound 8 mean 9 10 White British 5853 3352.51 5.13 3375.66 6.43 3363.07 3388.26 11 12 Indian 840 3045.53 4.64 3073.08 16.56 3040.62 3105.55 13 Pakistani 4013 3164.89 4.71 14 3130.71 7.65 3115.72 3145.71 15 BangladeshiFor 1689 peer3080.75 review5.14 3068.01 only 11.7 3045.09 3090.93 16 17 18 aAdjusted for maternal age, smoking status, diabetes, gestation age at delivery and maternal height, BMI and 19 parity 20 21 22 23 24 Bonferroni post hoc analysis revealed adjusted mean birthweight was statistically 25 26 significantly lower in Indian (M = 3073.08. SE = 17.83), Pakistani (M = 3130.71 SE = 27 28 29 10.74) and Bangladeshi (M = 3068.01 , SE = 13.62) compared with white British infants (M 30 31 =3375.66, SE = 6.43), a mean difference of 302.58g, 95% CI [255.53 349.62] p<.005, 32 33 (Indian), 307.65g 95% CI [271.72 343.59] p<.005 (Bangladeshi) and 244.95, 95% CI
34 http://bmjopen.bmj.com/ 35 [217.84 272.06] (Pakistani) p<.005. Moreover, differences in adjusted mean birthweight 36 37 were found between Indian and Pakistani infants 57.63g, 95% CI [ 105.85—9.41] p<.01 and 38 39 40 Pakistani and Bangladeshi infants 62.7 g 95% CI [26.44 98.96] p<.005, but no significance 41 42 was found between the adjusted mean birthweight of Indian and Bangladeshi infants. 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 As smoking is a recognised contributor for LBW, multiple regressions were conducted to 47 48 49 determine the variance of smoking on birthweight. The assumptions for multiple regressions
50 2 51 were checked and satisfied. The R for the model was .046. Smoking was found to 52 53 statistically predict lower birthweight F (2, 15,174) = 365.85, p < .0005 (see table 3). 54 55 56 57 58 59 60 11 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 12 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Table 3: Summary of multiple regressions 4
5 Variable B SEB β 6 Smoking status 242.25 16.23 .125 7 Ethnicity 50.52 1.93 .219
8 B = unstandardized regression coefficient, SEB = standard error of the coefficient, β = standardised 9 coefficient 10 11 12 13 Next, Multiple regression was conducted to establish variance of PTB on birthweight, by 14 15 For2 peer review only 16 ethnicity. The R varied according to ethnicity between .222 and .288, the cohort model was 17 2 2 2 18 .26, R for Bangladeshi infants was .236, R for Pakistani infants was .234, WB infants R = 19 20 .288 and for Indian infants the R2 =.222. The ANOVA was significant in all ethnic groups. 21 22 WB infants was, F(1, 7015) = 2831.84, p < .001, Indian infants was F(1, 989) = 282.25, p < 23 24 .001, Pakistani infants is reported as F(1, 1539) = 1844.75, p < .001 and Bangladeshi infants 25 26 27 is also reported as F(1, 2055) = 634.52, p < .001. 28 29 30 31 A binary logistic regression procedure was used to examine the relationship between 32 33 ethnicity and PTB. An overall significant relationship was observed (χ2 (7.85) = df 3 p =
34 http://bmjopen.bmj.com/ 35 36 <.05. Using the White British category as a comparison, it was found that the Indian ethnic 37 38 group was significantly over represented in terms of PTB (W = 8.192, df 1, p =.004) The 39 40 Exp(B)/OR value was 1.621 (95% CI 1.165 – 2.258). 41 42
on October 1, 2021 by guest. Protected copyright. 43 44
45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 12 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 13 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 4 Discussion: 5 The aim of this paper was to identify differences in birthweight and gestation age at delivery 6 7 between Indian, Pakistani and Bangladeshi and white British women. Differences between 8 9 10 the mean birthweights of Indian, Pakistani, Bangladeshi and white British infants were found, 11 12 in addition to an association between pre term delivery in primapara Indian mothers. The 13 14 results showed that there was a difference of 307.65g between WB and Bangladeshi infants. 15 For peer review only 16 This is consistent with previous results, showing that South Asian infants are 230 250 g 17 18 19 lighter [14–16]. Moreover, a small difference ranging from 57.63 62.7 g was also identified 20 21 between Indian, Bangladeshi and Pakistani infants, although this marginal difference is likely 22 23 not be clinically useful. 24 25 26 27 28 29 The results showed that Indian infants had the lightest unadjusted mean birth weights, 30 31 followed by Bangladeshi, Pakistani and white British infants respectively. However, after 32 33 controlling for known confounders, Bangladeshi infants were found to have the lightest mean
34 http://bmjopen.bmj.com/ 35 36 birthweight. Not unexpectedly, maternal smoking, maternal height, BMI and parity showed a 37 38 significant independent contribution to the outcome of infant birthweight. Furthermore, an 39 40 association was found between primipara Indian mothers and pre term delivery, within this 41 42 cohort. on October 1, 2021 by guest. Protected copyright. 43 44 45 46 47 48 Leon and Moser[14] also found Bangladeshi infants were the lightest, compared with Indian, 49 50 51 Pakistani or white British infants. On the other hand, the MCS[12] calculated birthweight 52 53 gestation age at delivery using self reported data and found that the unadjusted mean 54 55 birthweight was lightest in Indian infants, followed by Bangladeshi, Pakistani and white 56 57 British respectively. Furthermore, the adjusted mean calculations showed a number of 58 59 60 13 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 14 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 different findings according to the variables controlled; maternal and infant factors (i.e. 4 5 gestation age, parity, maternal height and weight and antenatal complications) found 6 7 Pakistani infants were lightest, whereas when controlling for behavioural factors (i.e. 8 9 10 antenatal care, smoking and drinking) and socioeconomic factors (i.e. household income, 11 12 education status, occupation status, single parentage, and housing tenure) showed Indian 13 14 infants were lightest. Margetts et al[4], results also showed that infants delivered to mothers 15 For peer review only 16 born in India had lighter infants, while Pakistani born mothers had heavier infants, however, 17 18 19 their results were only adjusted for generation status, therefore the mean weight reported in 20 21 the paper is unadjusted. 22 23 24 Taken together, this is suggestive that birthweight might be sensitive to different 25 26 combinations of mediators, which may vary according to maternal ethnicity, an important 27 28 point for specific antenatal interventions[40]. Moreover, a further explanation of the results 29 30 found in this study is that that birthweight is sensitive to environmental influences and the 31 32 33 national level figures used in Leon and Moser’s analysis will average out regional variations,
34 http://bmjopen.bmj.com/ 35 as evidenced in the current paper, which focuses on mean birthweights specifically in 36 37 Luton[14,41]. Furthermore, these results fail to support the current explanation that South 38 39 Asian infants are lighter as a consequence of their parents being of a smaller stature 40 41 42 [19,46,47], since BMI at booking and maternal height was controlled and adjusted mean 43 on October 1, 2021 by guest. Protected copyright. 44 birthweight was still found to be significantly lighter in all South Asian ethnicities, compared 45 46 with WB. 47 48 49 While Patel and colleagues used a large South Asian sample size (n=16 192) found an 50 51 increased OR for South Asian mothers having a pre term birth in their study[18], they 52 53 54 aggregated Pakistani, Bangladeshi and Indian mothers, which obscured any sub group trends. 55 56 However, our study assessed pre term delivery in primapara Pakistani, Bangladeshi Indian 57 58 and white British mothers and found a significant association between pre term delivery and 59 60 14 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 15 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Indian mothers; although it is recognised that socioeconomic factors were not controlled in 4 5 this cohort. 6 7 8 The MCS also showed that Indian mothers had a higher rate of preterm birth compared to 9 10 Pakistani and Bangladeshi mothers, however, similar to the present study, the analyses was 11 12 13 restricted to a binary outcome of births 24 37 weeks of gestation and after 37 weeks of 14 15 gestation (henceFor excluding peer pre viable births).review Therefore, this only results in the loss of some 16 17 information; exclusion of pre viable births (i.e. <24 weeks of gestation) means that it is 18 19 impossible to compare the frequency of early pregnancy loss by maternal ethnicity[12]. 20 21 22 Higher rates of early loss may well be evident in Pakistani mothers, due to a higher 23 24 prevalence of congenital anomalies, some of which may be lethal, but this as yet needs to be 25 26 elucidated[42]. 27 28 29 Taken together these results highlight a number of key findings. Firstly that there are 30 31 important differences between Pakistani, Bangladeshi and Indian infant birthweights, 32 33 whereby treating them in research terms as a homogenous group categorised as ‘South Asian’
34 http://bmjopen.bmj.com/ 35 36 obscures distal determinants. Researchers should move away from using the category of 37 38 ‘South Asian’ and be more specific about ethnicity when reporting populations under study. 39 40 Secondly, when comparing the findings with previous studies [4,12,18,43], this study shows 41 42 that the confounding variables controlled for also influences the results of which maternal on October 1, 2021 by guest. Protected copyright. 43 44 45 ethnicity has the lightest mean birthweight; suggestive that a closer examination of maternal 46 47 and behavioural mediators is warranted. It is possible that contributors for LBW in one 48 49 population are less pronounced in another and these factors need to be better understood. 50 51 Furthermore, while there are known trends such as LBW in South Asian mothers[27,28], 52 53 54 there are also clear ethnic and regional variations, suggestive of mediating social and 55 56 environmental factors, which warrant further investigation. 57 58 59 60 15 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 16 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 This study has a number of strengths; the large sample sizes of the Indian, Pakistani and 4 5 Bangladeshi mothers, compared to the MCS[12], whereby the authors over sampled from 6 7 BAME populations, actually had smaller sample sizes from Indian (n = 433), Pakistani (n= 8 9 10 687) and Bangladeshi mothers (n= 215) than the present study, whose subgroup sample size 11 12 is substantially larger, providing more generalisable results. In addition, it accesses 5 years’ 13 14 worth of data, which provides a more reliable picture and addresses any cohort anomalies that 15 For peer review only 16 may occur in shorter duration datasets. 17 18 19 This study is not without limitations. Hypertension in pregnancy is known to contribute to 20 21 22 growth restriction, placental problems and increase maternal mortality risk. However, in this 23 24 cohort, the data reported only 12 cases; therefore while this was excluded from analysis it 25 26 may have had a clinical impact which not accounted for. Furthermore, while the sample sizes 27 28 for Indian, Pakistani and Bangladeshi mothers was larger than the MCS, our Indian sample 29 30 size was still relatively small. In addition, there were no socioeconomic measures available to 31 32 33 the research team to allow controlling of socioeconomic factors known to mediate pre term
34 http://bmjopen.bmj.com/ 35 birth in this study. It would be beneficial for future research to investigate further trends in 36 37 pre term birth and Pakistani, Bangladeshi and Indian infants, while controlling for 38 39 socioeconomic factors, especially as there are known differences in the socioeconomic status 40 41 42 between Indian, Pakistani and Bangladeshi ethnic groups in England[44]. 43 on October 1, 2021 by guest. Protected copyright. 44 45 In conclusion this study presents important differences in mean birthweights between Indian, 46 47 Pakistani and Bangladeshi infants. Furthermore, an association between primapara Indian 48 49 mothers and pre term birth was found. LBW and PTB both contribute significantly to 50 51 mortality and morbidity outcomes, therefore understanding the reasons for this disparity is 52 53 54 essential for levelling up service provision and policy planning[20,21,45,46]. 55 56 57 58 59 60 16 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 17 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Acknowledgments 4 We would like to thank Martina McIntyre for extracting the de identified data from CMiS 5 6 and Tessa Pollard for her helpful comments on earlier drafts of this manuscript. 7 8 Competing Interests 9 10 The authors declare that there are no competing interests. 11 12 Contributions 13 14 RG and NA conceived the study; MG assisted in identification of data, RG and AG 15 conducted theFor statistical analyses,peer RG, NA,review GR, AG, and MG contributedonly to earlier drafts of 16 the manuscript and all authors agreed the final version. 17 18 19 Funding 20 The Steel Trust has provided funding to the University of Bedfordshire for RG to undertake 21 research at Institute for Health Research, University of Bedfordshire, under the direction of 22 NA and GR. The funders have no involvement in the research or publication. 23 24 Data sharing statement 25 26 27 No additional data are available 28 29 30 31 32 33
34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 17 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 18 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 References 4 1 Messer J. An analysis of the socio demographic characteristics of sole registered births 5 6 and infant deaths. Health Stat Q 2011;:79–107. doi:10.1057/hsq.2011.9 7 2 Institute of Health Economics. Determinants and Prevention of Low Birth Weight : A 8 Synopsis of the Evidence. Alberta, Canada: 2008. 9 10 3 De Farias Aragão VM, Barbieri MA, Moura Da Silva AA, et al. Risk factors for 11 intrauterine growth restriction: a comparison between two Brazilian cities. Pediatr Res 12 2005;57:674–9. doi:10.1203/01.PDR.0000156504.29809.26 13 14 4 Margetts BM, Yusof SM, Dallal Z Al, et al. Persistence of lower birth weight in 15 secondFor generation peerSouth Asian babies review born in the UK. J onlyEpidemiol Community Health 16 2002;56:684–7. 17 18 5 Joshi K, Sochaliya KM, Shrivastav A V, et al. A hospital based study on the 19 prevalence of low birth weight in newborn babies and its relation to maternal health 20 factors. Int J Res Med 2014;3:4–8. 21 22 6 World Health Organisation. Promoting Optimal Fetal Development: Report of a 23 Technical Consultation. Geneva: 2006. 24 http://www.who.int/nutrition/publications/fetal_dev_report_EN.pdf 25 26 7 Kramer MS. Determinants of low birth weight : methodological assessment and meta 27 analysis. Bull World Health Organ 1987;65:663– 28 737.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2491072/pdf/bullwho00076 29 0086.pdf 30 31 8 Escobar GJ, Littenberg B, Petitti DB. Outcome among surviving very low birthweight 32 infants : a meta analysis. Arch Dis Child 1991;66:204–11. 33 9 Blencowe H, Cousens S, Chou D, et al. Born too soon: the global epidemiology of 15
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34 http://bmjopen.bmj.com/ 35 study. Eur J Public Health 2014;2008:1–6. doi:10.1093/eurpub/cku059 36 24 Han Z, Mulla S, Beyene J, et al. Maternal underweight and the risk of preterm birth 37 and low birth weight : a systematic review and meta analyses. Int J Epidemiol 38 39 2011;40:65–101. doi:10.1093/ije/dyq195 40 25 Loret de Mola C, Araújo de França GV, Quevedo LDA, et al. Low birth weight, 41 preterm birth and small for gestational age association with adult depression: 42 43 systematic review and meta analysis. Br J Psychiatry 2014;205:340–7. on October 1, 2021 by guest. Protected copyright. 44 doi:10.1192/bjp.bp.113.139014 45 26 Office for National Statistics. Statistical Bulletin Births in England and Wales by 46 Parents’ Country of Birth: 2013. 2014. 47 48 27 Harding S, Rosato MG, Cruickshank JK. Lack of change in birthweights of infants by 49 generational status among Indian, Pakistani, Bangladeshi, Black Caribbean, and Black 50 African mothers in a British cohort study. Int J Epidemiol 2004;33:1279–85. 51 doi:10.1093/ije/dyh186 52 53 28 Moser K, Stanfield KM, Leon D a. Birthweight and gestational age by ethnic group, 54 England and Wales 2005: introducing new data on births. Health Stat Q 2008;:22–31, 55 34–55.http://www.ncbi.nlm.nih.gov/pubmed/18810886 56 57 29 Office for National Statistics. Statistical Bulletin Childhood, Infant and Perinatal 58 59 60 19 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 20 of 23 BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 Mortality in England and Wales, 2012. 2012. 4 http://www.ons.gov.uk/ons/rel/vsob1/child mortality statistics childhood infant and 5 perinatal/2012/ 6 7 30 Kent ST, McClure L a, Zaitchik BF, et al. Area level risk factors for adverse birth 8 outcomes: trends in urban and rural settings. BMC Pregnancy Childbirth 2013;13:129. 9 doi:10.1186/1471 2393 13 129 10 11 31 Yadav H, Lee N. Maternal factors in predicting low birth weight babies. Med J 12 Malaysia 2013;68:44–7. 13 14 32 Garcia RL, Ali N, Papadopoulos C, et al. Specific antenatal interventions for Black, 15 AsianFor and Minority peer Ethnic (BAME) review pregnant women at onlyhigh risk of poor birth 16 outcomes in the United Kingdom: A scoping review. BMC Pregnancy Childbirth 17 Published Online First: 2015.http://www.biomedcentral.com/1471 2393/15/226 18 19 33 Kim D, Saada A. The social determinants of infant mortality and birth outcomes in 20 western developed nations: A cross country systematic review. Int J Environ Res 21 Public Health 2013;10:2296–335. doi:10.3390/ijerph10062296 22 34 Cresswell J a, Yu G, Hatherall B, et al. Predictors of the timing of initiation of 23 24 antenatal care in an ethnically diverse urban cohort in the UK. BMC Pregnancy 25 Childbirth 26 2013;13:103.http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3652742&too 27 l=pmcentrez&rendertype=abstract 28 29 35 Ravelli ACJ, Tromp M, Eskes M, et al. Ethnic differences in stillbirth and early 30 neonatal mortality in The Netherlands. J Epidemiol Community Health 2011;65:696– 31 701. doi:10.1136/jech.2009.095406 32 36 Freemantle J, Wood C, Griffin C, et al. What factors predict differences in infant and 33 perinatal mortality in primary care trusts in England? A prognostic model. BMJ
34 http://bmjopen.bmj.com/ 35 2009;339:b2892. doi:10.1136/bmj.b2892 36 37 Silverwood RJ, Pierce M, Hardy R, et al. Low birth weight, later renal function, and 37 the roles of adulthood blood pressure, diabetes, and obesity in a British birth cohort. 38 39 Kidney Int 2013;84:1262–70. doi:10.1038/ki.2013.223 40 38 Department of Health. Data standards: Ethnic category. 2008. 41 http://webarchive.nationalarchives.gov.uk/+/http://www.isb.nhs.uk/documents/dscn/ds 42 43 cn2008/dataset/112008.pdf on October 1, 2021 by guest. Protected copyright. 44 39 Economic and Social Data Service. Ethnicity : Introductory User Guide. 2012. 45 http://www.esds.ac.uk/government/docs/ethnicityintro.pdf 46 47 40 Garcia RL, Ali N, Papadopoulos C, et al. Specific antenatal interventions for Black, 48 Asian and Minority Ethnic (BAME) pregnant women at high risk of poor birth 49 outcomes in the United Kingdom: A scoping review. BMC Pregnancy Childbirth 50 Published Online First: 2015.http://www.biomedcentral.com/1471 2393/15/226 51 52 41 Enkin M, Chalmers I. Effectiveness and satisfaction in antenatal care. In: Enkin U, 53 Chalmers I, eds. Antenatal Care. London: : Heinemann Medical. 1982. 266–90. 54 55 42 Kurinczuk JJ, Hollowell J, Boyd PA, et al. The contribution of congenital anomalies to 56 infant mortality. 2010. 57 58 43 Leon DA, Moser KA. Low birth weight persists in South Asian babies born in England 59 60 20 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 21 of 23 BMJ Open BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from 1 2 3 and Wales regardless of maternal country of birth. Slow pace of acculturation, 4 physiological constraint or both? Analysis of routine data. J Epidemiol Community 5 Heal 2012;66:544–51. doi:10.1136/jech.2010.112516 6 7 44 Platt L. Inequality within ethnic groups. 2011. 8 http://www.jrf.org.uk/sites/files/jrf/inequality ethnicity poverty full.pdf 9 10 45 Whitehead M, Dahlgren G. Concepts and principles for tackling social inequities in 11 health : Levelling up Part 1. World Heal Organ 2007;:1– 12 45.http://www.euro.who.int/__data/assets/pdf_file/0010/74737/E89383.pdf 13 14 46 Dahlgren G, Whitehead M. European strategies for tackling social inequities in 15 health:For Levelling uppeer part 2. World review Health Organisation 2007.only 16 http://www.euro.who.int/__data/assets/pdf_file/0018/103824/E89384.pdf 17
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34 http://bmjopen.bmj.com/ 35 36 37 38 39 40 41 42 43 on October 1, 2021 by guest. Protected copyright. 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 21 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open: first published as 10.1136/bmjopen-2017-017139 on 11 August 2017. Downloaded from Page 22 of 23 6 6
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