Abstract
Induced abortion (IA) has been associated with a lower risk of preeclampsia among nulliparous women, but it remains unclear whether this association differs by method (either surgical or medical) or timing of IA. We performed a nested case-control study of 12,650 preeclampsia cases and 50,600 matched control deliveries identified in the Medical Birth Register of Finland from 1996 to 2010. Data on number, method, and timing of IAs were obtained through a linkage with the Registry of Induced Abortions. Odds ratios and 95% confidence intervals were calculated. Overall, prior IA was associated with a lower risk of preeclampsia, with odds ratios of 0.9 (95% confidence interval (CI): 0.9, 1.0) for 1 prior IA and 0.7 (95% CI: 0.5, 1.0) for 3 or more IAs. Differences in the associations between IA and preeclampsia by timing and method of IA were small, with odds ratios of 0.8 (95% CI: 0.6, 1.1) for late (≥12 gestation weeks) surgical abortion and 0.9 (95% CI: 0.7, 1.2) for late medical abortion. There was no association between IA in combination with a history of spontaneous abortion and risk of preeclampsia. In conclusion, prior IA only was associated with a slight reduction in the risk of preeclampsia.