Demographic, lifestyle, and reproductive risk factors for ectopic pregnancy.

OBJECTIVE: To evaluate the relationship between demographic, lifestyle, and reproductive factors and the risk of ectopic pregnancy (EP).

DESIGN: Prospective cohort.

SETTING: United States.

PATIENT(S): Nurses' Health Study II cohort comprising 41,440 pregnancies from 22,356 women.

INTERVENTION(S): Demographic, lifestyle, and reproductive factors self-reported in 1989 then updated every 2 years. Multivariable log-binomial regression models with generalized estimating equations were used to estimate adjusted risk ratios (aRR).

MAIN OUTCOME MEASURE(S): Ectopic pregnancy.

RESULT(S): Incident EP was reported in 411 (1.0%) pregnancies. Former and current smokers had 1.22 (95% confidence interval [CI], 0.97-1.55) and 1.73 (95% CI, 1.28-2.32) times, respectively, the risk of EP compared with never smokers. The risk of EP 10 years after quitting was similar to never smokers (aRR 0.90; 95% CI, 0.60-1.33). Women consuming ≥10 g/day of alcohol had 1.50 (95% CI, 1.08-2.09) times the risk of EP compared with never consumers. In utero exposure to diethylstilbestrol (aRR 3.55; 95% CI, 2.51-5.01), earlier initiation of oral contraceptives (aRR 2.64; 95% CI, 1.70-4.09 for <16 years vs. never), intrauterine device use (aRR 3.99; 95% CI, 2.06-7.72), or history of infertility (aRR 3.03; 95% CI, 2.48-3.71) or tubal ligation (aRR 16.27; 95% CI, 11.76-22.53) also were associated with a higher risk of EP.

CONCLUSION(S): Women who were current or former smokers, consumed ≥10 g/day of alcohol, were exposed to diethylstilbestrol in utero, initiated oral contraceptives at earlier than age 16 years (which may be a marker of riskier sexual behaviors), and who had a history of infertility, intrauterine device use, or tubal ligation had a higher risk of EP.