Risk factors for ectopic pregnancy: a meta-analysis

OBJECTIVE: To review current knowledge on the risk of ectopic pregnancy (EP), with the exception of contraceptive methods.

DESIGN: Meta-analysis.

SETTING: Case control and cohort studies published between 1978 and 1994 in English, French, German, or Dutch, retrieved by Medline search, crossover search from the papers obtained, and hand-search on recent medical journals.

PATIENTS: A total number of 6,718 cases of EP in 27 case control studies and 13,049 exposed women in 9 cohort studies.

MAIN OUTCOME MEASURES: Detected studies were tested for homogeneity. If homogeneity was not rejected, Mantel-Haenszel common odds ratios (OR) and 95% confidence intervals were calculated.

RESULTS: Previous EP, previous tubal surgery, documented tubal pathology, and in utero diethylstilbestrol (DES) exposure were found to be associated strongly with the occurrence of EP. Previous genital infections (pelvic inflammatory disease [PID], chlamydia, gonorrhoea), infertility, and a lifetime number of sexual partners > 1 were associated with a mildly increased risk. For gonorrhoea, PID, previous EP, previous tubal surgery, and smoking, a higher common OR was calculated when using pregnant controls compared with using nonpregnant controls.

CONCLUSIONS: The strong risk in women with a previous EP, previous tubal surgery, documented tubal pathology, or in utero DES exposure justifies the exploration of a screening policy for EP among these women. If a risk factor reduces fertility chances, the OR detected when using pregnant controls is higher than the OR calculated using nonpregnant controls.