Background factors of ectopic pregnancy. I. Frequency distribution in a case-control study.

Two hundred and five patients with ectopic pregnancy in a well-defined Swedish population were interviewed with respect to prior disease and pregnancy histories as well as various constitutional and socioeconomic factors. The results were compared with those of two control groups, i.e. 110 early pregnant women intending to continue the gestation to term as well as 101 women seeking voluntary interruption of pregnancy. The results provide evidence that several may be involved in the etiology of ectopic pregnancy, including abdominal (or pelvic) surgery, previous ectopic pregnancy and pelvic inflammatory disease. Furthermore, a history of infertility is strongly correlated to ectopic pregnancy. On the other hand, there is no evidence that uncomplicated spontaneous or induced abortion, parity or marital status are important factors.