Genetics of obstetrical variables. A study from the collaborative perinatal project*

Abstract

Several obstetric variables were examined for genetic correlation in data from more than 8200 women (roughly 60 % black and 40 % white) linked into about 3200 family groups by birth or marriage and registered in the Collaborative Perinatal Project. Sister‐in‐law pairs yielded estimates of non‐genetic and spurious correlations which were generally absent or low. Pairs of sisters, mothers and daughters, half sisters, first cousins, and aunts and nieces were compared; such relatives were also compared in certain combinations of three. Familial correlation was present for age at menarche and durations of stages 1 and 3 of labor. None was found for gestation time of livebirths or for stage 2 of labor. A significant sister correlation for diagonal conjugate (size of pelvic inlet) was apparent in the white, but not the black, sample. No families had two or more occurrences of the infrequent conditions: thrombosis, infertility diagnosis, incompetent cervix, leiomyoma, hyperemesis gravidarum, hydramnios, placenta praevia, or prolapsed cord. Familial correlation was significant for fetal death risk, but not for bleeding during pregnancy, abnormal presentation of the fetus, abruptio placentae, breast abnormalities and hypertension. Familial associations for anemia, postpartum hemorrhage, varicose veins and albuminuria were significant in the black data, but not in the smaller white sample. There was a positive, but non‐significant, association of toxemia in sisters.