Neither the cause nor the effect of severe vomiting during pregnancy is well understood. This study examines possible causes of severe vomiting and associations between this disorder and fetal outcomes. One thousand eight hundred sixty-seven women with normal singleton live births were included in the analysis. The cumulative incidence of severe vomiting during pregnancy was 10.8%. Women with chronic liver disease had a threefold increased risk of severe vomiting during pregnancy. Paternal smoking was associated with a twofold increased risk of maternal vomiting. A modest association between severe vomiting and fetal growth retardation was identified (OR = 1.4, 95% CI: 0.9-2.3). Severe vomiting was also found to be associated with preeclampsia (OR = 1.5, 95% CI: 1.0-2.4). Our study indicates that passive smoking is a risk factor for vomiting during pregnancy, which may, in turn, increase the risk of fetal growth retardation.