Risk factors of ectopic pregnancy.
To assess the risk factors of ectopic pregnancy in Thai women. Department of Obstetrics and Gynaecology, Faculty of Medicine, Chulalongkorn University. Case controlled study. From 1999 to 2000, 208 cases of ectopic pregnancy and 781 controls (postpartum women) were included in the study. The women were interviewed by trained research interviewers using a standardized questionnaire. Detailed information regarding age at first intercourse, number of sexual partners, history of changing partners within 6 months, previous obstetric history, history of spontaneous and criminal abortion, history of pelvic inflammatory disease, smoking, history of endometriosis and history of previous ectopic pregnancy was collected. By multivariate analysis, 5 variables remained as strong and independent risk factors for ectopic pregnancy: the number of sexual partners > or = 2 (OR = 3.02, 95% CI (1.75-5.23), vaginal delivery > or = 1 (OR = 0.005, 95% CI (0.002-0.0015), history of pelvic inflamatory disease (OR = 3.17, 95% CI (1.40-7.19), smoking (OR = 2.49, 95% CI (1.36-4.55), infertility (OR = 2.74, 95% CI (1.35-5.54)). Problems of multiple sexual partners, pelvic inflammatory disease, smoking and infertility were the main risk factors of ectopic pregnancy in Thai women.