Does induced abortion increase the risk of preterm birth? Results from a case-control study

Aims: We analyzed the association between previous induced abortions and risk of preterm birth. Methods: This was a case-control study. Cases were 502 women who delivered preterm babies at the Clinica Luigi Mangiagalli and the Obstetric and Gynecology Clinic of the University of Verona. Controls were 1,966 women who gave birth at term (>= 37 weeks of gestation) to healthy infants of normal weight. Results: The odds ratio for all preterm births was 0.7 (95% CI 0.5-1.1) for women reporting 1 induced abortion and 1.6 (95% CI 0.7-3.5) for those reporting 2 or more induced abortions (chi(2) trend p = 0.81). Previous induced abortions did not increase the risk of preterm birth, both in small and normal for gestational age preterm infants. No difference emerged in risk factors for infants born at <32 and 32-36 gestational weeks. Conclusion: This study does not support the suggestion that induced abortions, as performed in Italy during the study period, increase the risk of preterm delivery in subsequent pregnancies.