Congenital malformations in singleton and twin births in rural Nigeria.

Background: The presence of a congenital malformation at birth is a cause of anxiety at an otherwise joyous occasion. Congenital malformations are a significant contributor to perinatal mortality.

Study Design: A retrospective study of external congenital abnormalities in singleton and twin births in rural eastern Nigeria over a 20 year period.

Result: The incidence of congenital defects for all deliveries was 110.8/10,000 births. Of 1453 twins and 32206 singleton births, there were 58 and 315 congenital abnormalities, with incidence of 97.8/10,000 births and 399.2/10,000 births respectively. Twins were significantly (x(2) =115.22; p< 0.0000) more likely to have a congenital malformation than singletons (RR 4.08, 95% CI 3.10 - 5.7). The pattern of defects was similar for singleton and twin births and the leading system affected was the musculo-skeletal system, distantly followed by the central nervous system. For both groups the commonest malformation was ulnar polydactyly, followed by hydrocephaly and ankyloglossia. Surprisingly no conjoined twins were recorded and there were only 7 cases of congenital umbilical hernia, abnormalities previously considered to be very common in Nigerians and Africans respectively.

Conclusion: Twins are about four times more likely to have congenital malformations than singletons. The overall prevalence of congenital malformations recorded is comparatively low. There is need for more detailed routine documentation of all birth defects including post-mortem report and the conduct of prospective population-based epidemiological surveys of birth defects in Nigeria.