Duration of human singleton pregnancies in Ibadan, Nigeria.

Analysis of gestation length in an obstetric population of indigenous African women revealed a mean pregnancy duration of 274.8 days, which is similar to values recorded in women of African descent elsewhere, but about 1 week less than what generally has been reported in women of European ancestry and Japanese women. Factors associated with lower pregnancy duration among these women include increasing maternal age and gravidity, and the birth of a male infant. It is concluded that mean pregnancy duration in Nigerian women is shorter than the 280 days normally used in obstetric calculations. The consistent finding of a shorter length of gestation in these and other black women suggests earlier maturity of the fetoplacental unit. Earlier institution of antepartum fetal monitoring in women of African descent, particularly women > 30 years old and those with high parity, may reduce the risks of fetal morbidity and mortality attributable to postmaturity in their offspring.