Objective: To study the impact of previous induced abortions on preterm delivery, small for gestational age and low birthweight in subsequent pregnancies.
Design: Survey of a national sample of births in France in 1995.
Setting: All public and private maternity hospitals in France.
Population: 12,432 women who had a singleton live birth during one week.
Methods: Data were collected during the women's postpartum stay in hospital, partly obtained by interview and partly abstracted from hospital medical records. Rates of preterm delivery, small for gestational age and low birthweight were compared according to existence and number of previous induced abortions. Maternal age, parity, history of previous adverse pregnancy outcome, maternal weight before pregnancy, marital status, educational level, maternal employment status during pregnancy, nationality, smoking during the third trimester of pregnancy and antenatal care were controlled for using multiple logistic regression and polytomous logistic regression.
Results: Twelve percent of women reported one previous induced abortion, and 3% two or more. Previous induced abortion was associated with an increased risk of preterm birth (OR 1.4; 95% CI 1.1-1.8); the risk of preterm delivery increased with the number of previous induced abortions (OR 1.3; 95% CI 1.0-1.7 for one previous abortion and OR 1.9; 95% CI 1.2-2.8 for two or more). The relationship was the same for very preterm and moderately preterm deliveries and for spontaneous and indicated preterm deliveries. After controlling for potential confounders, the association between previous induced abortions and small for gestational age and low birthweight infants was no longer significant.
Conclusion: This study suggests that a history of induced abortion increases the risk of preterm delivery, particularly for women who have had repeated abortions. The respective role of the surgical and medical techniques used for induced abortions needs to be explored.