Objectives To evaluate the risk of very preterm birth (22–32 weeks of gestation) associated with previous induced abortion according to the complications leading to very preterm delivery in singletons.
Design Multicentre, case-control study (the French EPIPAGE study).
Setting Regionally defined population of births in France.
Sample The sample consisted of 1943 very preterm live-born singletons (<33 weeks of gestation), 276 moderate preterm live-born singletons (33–34 weeks) and 618 unmatched full-term controls (39–40 weeks).
Methods Data from the EPIPAGE study were analysed using polytomous logistic regression models to control for social and demographic characteristics, lifestyle habits during pregnancy and obstetric history. The main mechanisms of preterm delivery were classified as gestational hypertension, antepartum haemorrhage, fetal growth restriction, premature rupture of membranes, idiopathic preterm labor and other causes.
Main outcome measures Odds ratios for very preterm birth by gestational age and by pregnancy complications leading to preterm delivery associated with a history of induced abortion.
Results Women with a history of induced abortion were at higher risk of very preterm delivery than those with no such history (OR + 1.5, 95% CI 1.1–2.0); the risk was even higher for extremely preterm deliveries (<28 weeks). The association between previous induced abortion and very preterm delivery varied according to the main complications leading to very preterm delivery. A history of induced abortion was associated with an increased risk of premature rupture of the membranes, antepartum haemorrhage (not in association with hypertension) and idiopathic spontaneous preterm labour that occur at very small gestational ages (<28 weeks). Conversely, no association was found between induced abortion and very preterm delivery due to hypertension.
Conclusion Previous induced abortion was associated with an increased risk of very preterm delivery. The strength of the association increased with decreasing gestational age.