Placental abruption. Maternal risk factors and associated fetal conditions.

OBJECTIVE: To investigate maternal risk factors and fetal conditions associated with abruption.

METHODS: Prospective cohort study of 30,681 singleton pregnancies at least 28 weeks' gestation. Data collected by patient questionnaire at the first prenatal visit and by medical record review.

RESULTS: 307 women had abruption (1%). After adjustment, important maternal risk factors included age (in years; OR 1.03; 95% CL 1.00, 1.06; p = 0.04) and less than 12 years of education (OR 1.58; 95% CL 1.10, 2.25; p = 0.01). Each pack of cigarettes smoked per day increased the risk by approximately 40% (OR 1.39; 95% CL 1.09, 1.79; p = 0.009). If abruption occurred, the perinatal mortality rate was substantially higher in women who smoked at least one pack per day than in nonsmokers (RR 2.53; 95% CL 1.14, 5.61; p = 0.02). Abruption was also significantly associated with intrauterine growth retardation and fetal malformations. The increased malformation rate was due entirely to nearly a five-times increase in congenital heart defects (OR 4.63; 95% CL 2.49, 8.55; p = 0.00000014).

CONCLUSIONS: Heavier smoking increases the risk both of abruption and of perinatal death when abruption occurs. If the association between abruption and congenital heart defects is confirmed, early evaluation could lead to more prompt treatment of these malformations in infants delivered after abruption.