Maternal cigarette smoking and tubal pregnancy.

As part of a case-control study of tubal pregnancy, we sought to evaluate the potential etiologic role of maternal cigarette smoking. Between 1975-1979, 192 women who were treated for a tubal pregnancy in five Seattle hospitals were interviewed with regard to smoking habits and reproductive, contraceptive, and medical histories. For comparison, 459 Seattle-area women who delivered during the same period were also interviewed. Current cigarette smokers had a more than twofold increase in risk of tubal pregnancy (adjusted relative risk 2.2; 95% confidence interval 1.4-3.4) when compared with women who had never smoked. The risk for women who had stopped smoking before conception was 1.6 (95% confidence interval 1.0-2.8). There was no consistent trend between the risk of tubal pregnancy and the duration of smoking, average number of cigarettes smoked per day, age at which a woman began to smoke, pack-years of cigarettes smoked, or (among former smokers) the recency of smoking. Although several sources of bias in the present study may have created a spurious association between cigarette smoking and the occurrence of tubal pregnancy, it could well be that an increased risk of tubal pregnancy is yet another untoward consequence of cigarette smoking.