Reduced fecundability in women with prenatal exposure to cigarette smoking.

Animal studies have suggested that fertility may be impaired by transplacental exposures, but little is known about human prenatal exposures and subsequent adult reproduction. A possible relation between prenatal exposure to cigarette smoking and adult fecundability in women was explored, with the use of data from a prospective study of 221 North Carolina couples. These couples were recruited during 1983-1985, at the time they stopped using birth control in order to become pregnant. The relative fecundability of exposed compared with unexposed women was estimated by applying a discrete-time proportional probabilities model to the cycle-by-cycle conception rates. Women with prenatal exposure to their mother's cigarette smoking had reduced fecundability. The fecundability ratio associated with prenatal exposure to mother's smoking, adjusted for age, frequency of intercourse, current smoking status, age at menarche, and childhood exposure to cigarette smoking, was 0.5 (95% confidence interval 0.4-0.8). This association was not changed by further adjustment for other possible confounding variables, including educational level, reproductive history, body weight, and consumption of alcohol and caffeine. Thus, women whose mothers smoked while pregnant with them may be on average substantially less fecund than women whose mothers did not smoke during pregnancy.