The relationship of abruptio placentae with maternal smoking and small for gestational age infants.

A population-based case-control study was conducted to examine the relationship between maternal smoking and the occurrence of abruptio placentae and to assess the joint relationship of smoking and small for gestational age (SGA) status with abruption. Cases (N = 1089) reported on Washington state birth certificates from 1984-1986 were compared with randomly selected births (N = 2323) from the same period. The occurrence of placental abruption was associated with both smoking (relative risk = 1.6; 95% confidence interval 1.3-1.8) and SGA status (relative risk = 2.6; 95% confidence interval 2.0-3.3). The association with SGA status was identical for smokers and non-smokers. Thus, the increase of SGA infants in women whose pregnancies are complicated by abruption is not explained by maternal smoking, and in some cases may result from placental dysfunction induced by the process of placental separation.