Risk factors for ectopic pregnancy. A population-based study
P. A. Marchbanks, J. F. Annegers, C. B. Coulam, J. H. Strathy and L. T. Kurland
Reproductive Health, Centers for Disease Control, Atlanta.
To evaluate the association between ectopic pregnancy and 22 potential risk
factors, we conducted a population-based case-control study. The
investigation included 274 cases diagnosed from 1935 through 1982 in
residents of Rochester, Minn, and 548 matched controls selected from
live-birth deliveries. Risk factor information documented prior to the last
index menstrual period was obtained via medical record abstract. Univariate
matched analyses revealed nine variables associated with a significantly
elevated relative risk of ectopic pregnancy. Following conditional logistic
regression, four variables remained as strong and independent risk factors
for ectopic pregnancy: current intrauterine device use (relative risk,
13.7; 95% confidence interval, 1.6 to 120.6), a history of infertility
(relative risk, 2.6; 95% confidence interval, 1.6 to 4.2), a history of
pelvic inflammatory disease (relative risk, 3.3; 95% confidence interval,
1.6 to 6.6), and prior tubal surgery (relative risk, 4.5; 95% confidence
interval, 1.5 to 13.9). Theoretically, any condition that prevents or
retards migration of the fertilized ovum to the uterus could predispose a
woman to ectopic gestation. Further research is needed to clarify the
impact of other potential risk factors in the etiology of ectopic
pregnancy.
