Placental abruption among singleton and twin births in the United States: Risk factor profiles

The authors performed a population-based epidemiologic study to evaluate an d contrast risk factor profiles for placental abruption among singleton and twin gestations. Data were derived from linked US birth/infant death files for 1995 and 1996, comprising 7,465,858 singleton births and 193,266 twin births. The authors also evaluated effect modification between smoking and hypertension and the effect of a dose-response relation with number of ciga rettes smoked daily on abruption risk. Abruption was recorded in 5.9 per 1, 000 singleton births and 12.2 per 1,000 twin births. Risk factors for abrup tion among singleton and twin births, respectively, included preterm premat ure rupture of membranes (adjusted relative risks (RRs) = 4.89 and 2.01), e clampsia (RRs = 3.58 and 1.67), anemia (RRs = 2.23 and 2.33), hydramnios (R Rs = 2.04 and 1.66), renal disorders (RRs = 1.54 and 2.56), and intrapartum fever (>100 degreesF) (RRs = 1.17 and 1.69). Chronic hypertension (RR = 2. 38) and pregnancy-induced hypertension (RR = 2.34) were risk factors for ab ruption in singleton births but not in twin births. Number of cigarettes sm oked daily demonstrated a dose-response trend for abruption risk in singlet ons and twins. Abruption was more likely to occur among smokers with chroni c hypertension (RRs = 4.66 and 3.15) and eclampsia (RRs = 6.28 and 5.08). T he authors conclude that abruption is twice as likely to occur in twins as in singletons with differing risk factor profiles. This suggests that abrup tion in twins may result from different pathophysiologic processes.