The effect of cigarette smoking, Chlamydia trachomatis infection, and vaginal douching on ectopic pregnancy

We conducted a case-control study of the relation between ectopic pregnancy and three exposures of interest: cigarette smoking, previous chlamydial infection, and vaginal douching. Cases were women with surgically confirmed tubal ectopic pregnancy; controls were women with intrauterine pregnancy at 14 weeks' gestation or less. All women were between the ages of 18-40 and were cared for at the same hospital. Sixty-nine case women and 101 controls were interviewed and underwent serologic tests for Chlamydia trachomatis exposure. Cases were more likely than controls to be nulliparous, non-white, and unmarried and to report a high school education or less (P less than .05). The proportions of cases and controls who reported smoking during the month of conception were 51 and 20%, respectively. The adjusted odds ratio for smoking was 2.4 (95% confidence interval 1.2-5.1) when current smokers were compared with former smokers and women who had never smoked. The proportions of women who had previous chlamydial infection (immunoglobulin G [IgG] greater than 1:64) among cases and controls were 35 and 20% (adjusted odds ratio 1.3, 95% confidence interval 0.6-3.0). Overall, 28% of cases and 19% of controls douched once or more per month (adjusted odds ratio 0.8, 95% confidence interval 0.3-2.2). We conclude that current cigarette smoking may be associated independently with ectopic pregnancy and that smoking cessation before the month of conception may reduce this risk. For these women, previous chlamydial infection and vaginal douching did not appear to increase significantly the risk of ectopic pregnancy.