Controlled ovarian hyperstimulation as a risk factor for ectopic pregnancy.

As part of a case-control study of ectopic pregnancy, we evaluated the potential etiologic role of controlled ovarian hyperstimulation in a population with no previous history of ectopic pregnancy. Ovulation induction alone was associated with an increased risk of ectopic pregnancy (adjusted odds ratio = 3.98; 95% confidence interval 1.10-14.30). In contrast, ovulation induction for in vitro fertilization did not increase the risk further (adjusted odds ratio = 2.45; 95% confidence interval 0.54-11.13). These results suggest that hormonal factors may be involved in the development of ectopic pregnancy.