There is increasing concern over whether environmental exposures early in life may impact health in adulthood. Recent evidence suggests that prenatal or childhood exposure to cigarette smoke may result in poorer reproductive health later in life. Among 2,162 nonsmoking women recruited from three Boston, Massachusetts, clinics who underwent assisted reproductive treatments between 1994 and 2003, adjusted odds ratios for pregnancy outcomes in the initial treatment cycle were calculated in relation to self-reported childhood exposure to parental cigarette smoke. Women who reported having two parents who smoked during their childhood had increased odds of a spontaneous abortion compared with women reporting that neither parent smoked (adjusted odds ratio = 1.8, 95% confidence interval: 1.0, 3.0). A trend for increased risk was observed for women reporting that zero, one, or two parents smoked. In secondary analysis, the authors also found suggestive evidence for increased risk of failed embryo implantation among women reporting current secondhand tobacco smoke exposure. Future large studies of pregnancy loss are needed that can distinguish women's tobacco smoke exposure in childhood from that taking place in utero.