INT J TUBERC LUNG DIS 20(6):729–737 Q 2016 The Union http://dx.doi.org/10.5588/ijtld.15.0697 E-published ahead of print 12 April 2016 Antenatal and early life tobacco smoke exposure in an African birth cohort study A. Vanker,* W. Barnett,* K. Brittain,* R. P. Gie,† N. Koen,‡ B. Myers,§ D. J. Stein,‡ H. J. Zar* *Department of Paediatrics and Child Health, Red Cross War Memorial Children’s Hospital, and Medical Research Council (MRC) Unit on Child & Adolescent Health, University of Cape Town, Cape Town, †Department of Paediatrics and Child Health, Tygerberg Children’s Hospital, Stellenbosch University, Cape Town, ‡Department of Psychiatry and Mental Health and MRC Unit on Anxiety & Stress Disorders, University of Cape Town, Cape Town, §Alcohol Tobacco and Other Drug Research Unit, South African Medical Research Council and Department of Psychiatry and Mental Health, University of Cape Town, Cape Town, South Africa SUMMARY BACKGROUND: Exposure to tobacco smoke in African (32%) were active smokers on cotinine testing. At birth infants has not been well studied, despite the high burden and at 6–10 weeks of life, respectively 135/241 (56%) of childhood respiratory disease in these communities. and 154/291 (53%) infants had urine cotinine levels OBJECTIVE: To investigate the prevalence of antenatal indicating tobacco smoke exposure. Household smoking and early life tobacco smoke exposure and associations was prevalent and was associated with positive infant with infant birth outcomes in an African birth cohort, cotinine test results. Antenatal maternal smoking was the Drakenstein Child Health Study. associated with decreased infant birthweight-for-age Z- METHODS: Self-report questionnaires assessing mater- score (0.3, 95%CI 0.1–0.5). nal and household smoking were administered. Mater- CONCLUSION: Antenatal and early life tobacco smoke nal and infant urine cotinine testing was conducted exposure is highly prevalent in this community, and may antenatally, at birth and at 6–10 weeks of life to measure impact on birth outcomes and subsequent child health. tobacco smoke exposure. Multivariate regression mod- Smoking cessation interventions are urgently needed to els explored the associations between exposure to smoke reduce tobacco smoke exposure in African communities. and infant birth outcomes. KEY WORDS: tobacco smoke exposure; birth out- RESULTS: Of 789 pregnant women included, 250 comes; birth cohort; child health; maternal health EXPOSURE TO TOBACCO SMOKE is an impor- Cotinine, a biomarker of tobacco smoking and tant risk factor for childhood respiratory disease,1–3 exposure, has been used to both confirm and quantify and childhood morbidity and mortality worldwide.4,5 smoking and exposure in pregnant women.9,16,17 Infant Prenatal exposure is associated with an increased risk exposure during the first year of life has been assessed of pneumonia and of wheezing disorders,6–8 and may using blood, urine or hair cotinine measures.16,18–20 also lead to pre-term delivery and decreased birth- However, no studies have used infant cotinine mea- weight, predisposing infants to severe respiratory surements at birth to assess in utero tobacco smoke disease.9,10 Other maternal socio-economic and exposure, and few studies have used infant measures to psychosocial risk factors, including depression and evaluate early life exposure.16,18 Documenting exposure intimate partner violence (IPV), may also impact is especially relevant in low-and middle-income country infant birth outcomes.11–13 (LMIC) settings, which carry the highest burden of Tobacco smoke exposure often begins in utero with childhood respiratory illnesses. active or passive maternal smoking, and may We measured antenatal and early postnatal tobac- continue postnatally. Both prenatal and postnatal co smoke exposure, and investigated the association exposure adversely affect infant health. Nicotine between antenatal exposure and infant birth out- exposure may be directly toxic to the airways or comes in an African birth cohort study. may result in secondary impairment of lung growth due to decreased foetal breathing or cellular dam- METHODS age.14 Furthermore, adult smokers have a higher risk of respiratory infections, with increased risk of A prospective study of smoke exposure was under- pathogen transmission to child contacts.15 taken in pregnant women and infants enrolled in the Correspondence to: Aneesa Vanker, Department of Paediatrics and Child Health, Red Cross War Memorial Children’s Hospital, Klipfontein Road, Rondebosch, Cape Town, South Africa. e-mail: [email protected] Article submitted 16 August 2015. Final version accepted 10 December 2015. 730 The International Journal of Tuberculosis and Lung Disease Drakenstein Child Health Study.21 The site of the Urine cotinine testing study is located 60 km outside Cape Town, South Maternal and infant urine cotinine tests were Africa, in a semi-rural area with a population of low performed using the IMMULITEw 1000 Nicotine socio-economic status (SES).21 More than 90% of the Metabolite Assay Kit (Siemens Medical Solutions population obtain health care in the public sector, Diagnostics, Glyn Rhonwy, UK). This provided a which has a strong primary health care system. quantitative test using a competitive chemilumines- cent immunoassay, which contained solid-phase Study population, participants and procedure beads coated with polyclonal rabbit anti-cotinine Pregnant women at between 20 and 28 weeks’ antibody. The test had a calibration range of 10–500 gestation were consecutively enrolled using conve- ng/ml, with an analytical sensitivity of 2 ng/ml. Urine nience sampling at one of two primary health care cotinine levels were classified as ,10 ng/ml (non- clinics serving different populations: Newman (pre- smoker), 10–499 ng/ml (passive smoker/exposed) or dominantly mixed race) and Mbekweni (predomi- 7500 ng/ml (active smoker), according to the nantly Black African). A second antenatal study visit manufacturer’s directions. was completed at 28–32 weeks’ gestation. All Maternal urine was collected and tested at the deliveries took place at a single central public second antenatal study visit and at birth, with the hospital, Paarl Hospital. Thereafter, mother-infant higher result used to classify smoking levels. Infant dyads attended follow-up visits, including at 6–10 urine was collected at birth and at 6–10 weeks, either weeks’ postpartum.21 via a urine bag or by placing a cotton-wool ball in the diaper from which urine could then be squeezed. Self-reported measures Urine samples were transferred to a clean, preserva- Sociodemographic data were collected at enrolment tive-free, plastic container and transported at tem- using a questionnaire adapted from the South African peratures of between 28 and 88C to the accredited Stress and Health Study.22 A composite SES score was medical laboratory for testing. developed as an internal comparison of SES for this sample, and participants were categorised as lowest, Ethics low–moderate, moderate–high or highest SES.13 The study was approved by the Faculty of Health Maternal tobacco smoking and exposure were Sciences Human Research Ethics Committees of the assessed using self-report questionnaires at enrolment. University of Cape Town and of Stellenbosch Maternal smoking was quantified as pack-years, University (Cape Town, South Africa), and by the whereby one pack-year was defined as 20 cigarettes Western Cape Provincial Health Research Committee smoked daily for one year. Maternal nicotine depen- (Cape Town, South Africa). Written informed con- dence was assessed using the Fagerstrom¨ test, a well- sent was provided by mothers at enrolment. validated questionnaire that scores tobacco depen- dence as low, low to moderate, moderate or high.23 Statistical analysis The Alcohol, Smoking and Substance Involvement Tobacco smoking and exposure were compared Screening Test (ASSIST) was administered to assess across the recruitment sites using the v2 or the Fisher’s substance use and substance-related risk.24 Partici- exact tests for categorical variables and Wilcoxon pants were categorised as being at low, moderate or rank-sum tests (Mann-Whitney tests) for non-nor- high risk of tobacco-related health problems, and any mally distributed continuous variables. The sensitiv- self-reported antenatal alcohol use was document- ity and specificity of self-reported maternal smoking ed.24 Women who reported antenatal substance use was calculated using maternal urine cotinine as the were counselled about cessation. gold standard. The associations between household Comprehensive psychosocial data were collected and maternal smoking (self-reported and based on antenatally, including an assessment for depression urine cotinine) and infant urine cotinine were using the Beck Depression Inventory (BDI-II) and a assessed using v2 tests, with cotinine levels of 710 questionnaire for any IPV in the past year.11,13 ng/ml used to categorise infants as being exposed to tobacco smoke. Risk ratios (RRs) with 95% confi- Birth outcomes dence intervals (CIs) were calculated to determine the All births were attended by a member of the study strength of these associations. Infant weight-for-age team. Birth outcomes included birth weight, gesta- (WfA) Z-scores were calculated using the revised tional age and presence of respiratory or other Fenton preterm growth charts, and infants with a disease. Gestational age at delivery (in completed WfA Z-score ,10th percentile were classified as small weeks) was calculated from