Risk factors for ectopic pregnancy in women with symptomatic first-trimester pregnancies.

Objective: To evaluate the association between ectopic pregnancy (EP) and clinical and historical factors among women presenting with pain and/or bleeding in early pregnancy.

Design: Nested case-control study.

Setting: University medical center.

Patient(s): Women with symptomatic early pregnancies of unknown location presenting for care between January 1, 1990 and July 31, 1999.

Intervention(s): None.

Main Outcome Measure(s): Clinical and historical risk factors were compared between women with EP and women with ongoing intrauterine pregnancies or spontaneous abortions.

Result(s): The following factors were associated with increased risk of EP: prior EP (odds ratio, 2.98 [95% confidence interval, 1.88-4.73] for one prior EP and 16.04 [5.39-47.72] for 2 or more), pelvic inflammatory disease history (1.5 [1.11-2.05]), pain at presentation (1.42 [1.06-1.92]), vaginal bleeding at presentation (1.42 [1.04-1.93]), and hCG of 501-2,000 mIU/mL (1.73 [1.24-2.42]). Age younger than 25 years (0.59 [0.41-0.85]) and a history of abortion were protective from EP (0.58 [0.38-0.90]). Prior nontubal pelvic surgery, past intrauterine device use, prior cesarean section, and current cervical infection demonstrated no association with EP.

Conclusion(s): Evaluation of women with a symptomatic early pregnancy confirms and refutes some of the classical risk factors for EP. Prior EP is a strong risk factor, whereas pelvic inflammatory disease has an unexpected weak association. Previous abortion was found to have a negative association, whereas nontubal surgery, cesarean section, and a history of or concomitant cervical infection have no association. Knowledge of historical and clinical factors associated with EP may aid in early diagnosis.