Ethnic difference in duration of pregnancy.

It is suggested that the observed difference in duration of pregnancy between Blacks and Whites is partly physiological since it is not entirely explained by social inequities alone. This study compares women with well-defined gestational periods seeking attention at the Antoine Béclère Maternity Clinic. Group A consists of French women of European ancestry, Group B, those born in the French Antilles of mixed ancestry, and Group C black African women with insignificant European admixture. When compared to Group A, within each socio-economic class, group B and C have shorter gestational periods. These differences persist after adjustment for socio-economic variables, so that other explanations should be considered, specifically genetic determinants.