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.
PIP: The possible association between fecundability and women with prenatal exposure to cigarette smoking was investigated in a data set from a prospective study of 221 North Carolina couples. The relative fecundability of exposed versus unexposed women was estimated by applying a discrete-time proportional probabilities model to the cycle-by-cycle conception rates among these couples. A strong negative correlation between fecundability and prenatal exposure to cigarette smoking was observed in both the unadjusted and adjusted data. 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 significant association was not changed by further adjustments for other possible confounding factors such as educational level, reproductive history, body weight, and caffeine and alcohol consumption. 1 complication in the interpretation of these data is the correlation between prenatal and childhood smoking exposure. Any observed association of prenatal exposure to mother's smoking with fecundability could be due to childhood passive smoking exposure since most mothers who smoked during pregnancy also smoked after pregnancy. However, if this were the case, women exposed as children to only their father's smoking should show reduced fecundability. Instead, these women actually demonstrated increased fecundability. Thus, the data suggest that women whose mothers smoked while pregnant with them may be on average substantially less fecund than women whose mothers did not smoke during pregnancy.