IJHG May-Aug 07.Indd
Total Page:16
File Type:pdf, Size:1020Kb
59 Original Article Human sex ratio at birth in South West Nigeria M. A. Azeez*, A. Akinboro*^, A. A. Bakare^ Department of *Pure and Applied Biology, Ladoke Akintola University of Technology, P. M. B. 4000, Ogbomoso; ^Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan. Nigeria The sex ratio of man is expected to be more or less equal BACKGROUND: Human sex ratio at birth differs from one population to the other. This variation has been attributed because of the 1:1 segregation of X and Y-chromosomes to cultural practices, seasonal variation, small-family in the male.[2] In 2004, males accounted for 50.4% of the size policy and sex selective technology. Information on global total.[3] In the absence of manipulation, human secondary sex ratio in Nigeria is limited. AIMS AND OBJECTIVE: To analyzed human sex ratio secondary sex ratio is commonly assumed to be 105- at birth for samples of the Nigerian population in 4 urban 107 male births for every 100 female birth. However, settings in Southwest Nigeria, in order to know the trend and to compare the fi ndings with those of previous reports. sex ratios at birth or among infants may be considerably MATERIALS AND METHODS: Data were collected from skewed by sex-selective abortion and infanticide. Even Obafemi Awolowo University (OAU) teaching hospital at Ile in the absence of such practices, a range of sex ratios Ife and Wesley Guild hospital at Ilesa, Osun state; General hospital at Ogbomoso, Oyo state and Ekiti state specialist at birth of between 103 to 107 boys per 100 girls has hospital at Ado-Ekiti, Ekiti state. The data consisted of 35 been observed in different societies and among different 209 live single births recorded between 1995 and 2004. Each set of data was analyzed to determine the sex ratio ethnic and racial groups within a given society, though by year, month and quarterly values. Chi-square analysis more extreme ratios documented in some populations was used to determine the deviation of the sex ratios for should be attributed rather more to cultural preferences the years from the average value. RESULTS: The annual average ratios of 104.7:100, than to biological variation in the propensity to bear boys 102.8:100, 98.9:100 and 100.8:100 were recorded for or girls. OAU teaching hospital, Wesley Guild Hospital, General Hospital and Ekiti State specialist hospital, respectively. Darwin cites a sex ratio of 120 boys to 100 girls for When pooled together, the average ratio was 102.7:100. Jewish communities in 19th century Livonia, where This shows some bias for male births. Data also indicates more male birth in the rainy season, suggesting a seasonal infanticide is not historically documented and the variation of sex ratio. means for pre-natal sex determination did not exist.[1] CONCLUSION: These fi ndings are representative of the In the United States, the sex ratios at birth over the populations in southwest Nigeria and are comparable to values obtained for other regions in Nigeria (www.medknow.com).and other period 1970-2002 were 105 for the white non-Hispanic populations of African origin. population, 104 for Mexican Americans, 103 for African Key words: Birth/human sex ratio/Nigeria Americans and Indians and 107 for mothers of Chinese or This PDFa site is hosted available by forMedknow freeFilipino download ethnicity. Publications[4] Among from European countries, the ratios ranged between 104 in Belgium and 107 in Portugal. In the aggregated results of 56 Demographic and Health Introduction Surveys[5] in African countries, the ratio is 103, though there is also considerable country-to-country variation.[6] In Nigeria there is a strong social emphasis on Information on secondary sex ratio in Nigeria is limited. fertility and a tradition of son preference. Males and Ayeni[7] reported a value of 107.85:100 for Ibadan. females are produced in approximately equal numbers Effi ong et al.[8] noted a sex ratio of 106:100 among in most species with separate sexes regardless of the 31490 live-born Yoruba children delivered in Ibadan. mechanism of sex determination.[1] In humans, female is Boroffi ce[9] reported sex ratios of 107:100 for Ibadan and homogametic (XX) while the male is heterogametic (XY). 104:100 for the old Western states in Nigeria. Values Address for Correspondence: Dr. A. A. Bakare, Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan. Nigeria. E-mail: [email protected] Indian Journal of Human Genetics May-August 2007 Volume 13 Issue 2 60 Azeez, et al.: Sex ratio in South West Nigeria of 107:100 and 104:100 were obtained from Hausa Table 1: Annual sex ratio of live births recorded in Obafemi and Igbo population births, respectively.[10,11] The most Awolowo University Teaching Hospital Ile Ife, Osun State current report of data recorded up to 1995 noted an between 1995 and 2004 Year Males Females Total Sex ratio annual average sex ratio of 108.8:100 and 96:100 for 1995 943 915 1858 103.1:100 [2] Ibadan and Lagos, respectively. In order to know the 1996 851 853 1704 99.8:100 trend of sex ratio in Nigeria, this study was undertaken 1997 851 841 1692 101.2:100 to determine the secondary sex ratio of single live births 1998 827 828 1655 99.9:100 in samples of Nigerian population in southwest Nigeria 1999 689 692 1381 99.6:100 2000 739 675 1414 109.5:100 between 1995 and 2004 and compare the fi ndings with 2001 654 523 1177 125.0:100 those of previous reports. 2002 522 511 1033 102.2:100 2003 731 730 1461 100.1:100 Materials and Methods 2004 650 554 1204 117.3:100 Total 7457 7122 14579 104.7:100 Three states of southwestern Nigeria were considered insignifi cantly different from the average for the 10 years for this study. The Yoruba’s are the major ethnic group pooled together (χ2=6.8, df=9). The monthly sex ratio for in southwest Nigeria. Other ethnic groups such as this hospital over the years considered varied between the Hausa, Nupe and Fulani (from the north) and Ibo, 98.6:100 and 108.4:100 [Table 2]. The highest monthly Itshekiri, Efi k and Ijaw (from the south-east and south- sex ratio of 108.4:100 was recorded in September while south) are found in the minority. The data used were the lowest sex ratio of 98.6:100 was recorded in October. collected from the birth records of four different hospitals Table 2 presents the quarterly analysis of the data. The in urban areas of Osun, Oyo and Ekiti states. It consists third and last quarters had the highest and the lowest of births recorded for a period of 10 years (1995-2004). ratios of 106.6:100 and 100.1:100, respectively. These hospitals are Wesley Guild hospital at Ilesa, Osun Table 3 shows the annual secondary sex ratios of births state; Obafemi Awolowo University (OAU) teaching recorded in Wesley Guild hospital Ilesa, between 1995 and hospital at Ile-Ife, also in Osun state; General hospital at 2004. Average sex ratio of 102.8:100 was recorded for the Ogbomoso, Oyo state and Ekiti state specialist hospital at Ado-Ekiti, Ekiti state. Each set of data were analysed Table 2: Monthly and quarterly sex ratio of live births by year, month and quarterly values. All the data sets recorded in Obafemi Awolowo University Teaching were subsequently pooled together to determine the Hospital Ile Ife, Osun state between 1995 and 2004 annual sex ratio in southwestern Nigeria. (www.medknow.com).Secondary Month Males Females Total Sex ratio Jan. 644 611 1255 105.4:100 sex ratio was determined using the formula (x/y X 100): Feb. 566 546 1111 103.7:100 100 (where “x” is the number of male births and “y” is the Mar. 669 638 1307 104.9:100 number of femaleThis births). PDFa Chi-square site is hosted available analysis was by used forMedknow freeApr. download Publications674 from647 1321 104.3:100 to determine the deviation of the sex ratios for the years May 798 756 1554 105.6:100 from the average value at 0.05 level of signifi cance. Jun. 674 634 1308 106.3:100 Jul. 673 641 1314 105.0:100 Aug. 642 603 1245 106.6:100 Results Sept. 668 617 1285 108.4:100 Oct. 721 732 1453 98.6:100 Nov. 567 558 1125 101.6:100 The annual secondary sex ratios of births recorded Dec. 600 597 1197 100.6:100 in Obafemi Awolowo University teaching hospital Ile- ife, from 1995 to 2004 are presented in Table 1. The Quarter Males Females Total Sex ratio Jan-Mar. 1879 1795 3674 104.7:100 average sex ratio for the 10 years pooled together was Apr-Jun. 2146 2036 4182 105.4:100 104.7:100. The highest sex ratio of 125.0:100 was Jul-Sept. 1983 1860 3843 106.6:100 recorded in 2001 and the lowest sex ratio of 99.8:100 Oct-Dec. 1888 1886 3774 100.1:100 was recorded in 1996. The sex ratio for the years was χ2 = 0.23, df = 3, P<0.05 Azeez, et al.: Sex ratio in South West Nigeria 61 Table 3: Annual sex ratio of live births recorded in Wesley Table 5: Annual sex ratio of live births recorded in General Guild Hospital Ilesa, Osun state between 1995 and 2004 Hospital Ogbomoso, Oyo state between 1995 and 2004 Year Males Females Total Sex ratio Year Males Females Total Sex ratio 1995 533 494 1027 107.9:100 1995 254 257 511 98.8:100 1996 473 495 968 95.6:100 1996 241 214 455 112.6:100 1997 518 548 1066 94.5:100 1997 226 219 445 103.2:100 1998 620 608 1228 102.0:100 1998 160 154 314 103.9:100 1999 456 451 907 101.1:100 1999 160 159 319 100.6:100 2000 477 443 920 107.7:100 2000 187 196 383 95.4:100 2001 401 342 743 117.3:100 2001 175 197 372 88.8:100 2002 298 299 597 99.7:100 2002 241 231 472 104.3:100 2003 424 445 869 95.3:100 2003 254 281 535 90.4:100 2004 356 306 662 116.0:100 2004 339 355 694 95.5:100 Total 4556 4431 8987 102.8:100 Total 2237 2263 4500 98.9:100 ten-year period.