Objective: To analyse the relation between induced abortion and risk of subsequent miscarriage.
Design: Case-control study conducted between February 1990 and May 1995.
Participants: Case group included 782 women (median age 32 years, range 14-46) admitted for spontaneous abortion (within the 12th week of gestation) to a network of obstetric departments in the greater Milan area. The control group was recruited among women who gave birth at term (> 37 weeks of gestation) to healthy infants on randomly selected days at the hospitals where cases had been identified. A total of 1543 controls (median age 30 years, range 14-45) were interviewed.
Results: A total of 102 cases (13%) and 181 controls (12%) reported one or more induced abortions. No clear relation emerged between miscarriage and induced abortions. In comparison with women reporting no induced abortion the odds ratio (OR) for miscarriage were 1.1 (95% CI 0.8-1.4) in women reporting one induced abortion and 0.9 (95% CI 0.4-1.8) in women reporting two or more. Likewise, there was no association between time since last and age at first induced abortion and risk of miscarriage.
Conclusions: This study did not find any strong association between induced and spontaneous abortion.
PIP: The association between induced abortion and the risk of miscarriage in subsequent pregnancies was assessed in a case-control study conducted in Italy in 1990-95. 782 women (median age, 32 years) admitted to hospital obstetrics departments in Milan with spontaneous abortion in the first trimester of pregnancy were enrolled as cases, while 1543 women (median age, 30 years) who had a live, full-term birth at the same hospitals served as controls. Compared to controls, women with a spontaneous abortion were significantly more likely to be unmarried, to have a low educational level, and to have a history of pelvic inflammatory disease and previous miscarriage. 102 cases (13%) and 181 controls (12%) reported 1 or more induced abortions. Compared with women reporting no induced abortion, the odds ratio for miscarriage was 1.1 (95% confidence interval (CI), 0.9-1.4) in women reporting 1 induced abortion and 0.9 (95% CI, 0.4-1.8) in women reporting 2 or more induced abortions. Thus, this study failed to document a significant association between induced and spontaneous abortion. Moreover, there was no relationship between time since last induced abortion or age at first induced abortion and risk of miscarriage.