Background: Relationships between the severity of nausea and vomiting during pregnancy and selected demographic (employment status, parity, age, smoking) and pregnancy outcome (birthweight, gender) variables are described. Methods: Women who volunteered for a community-based clinical trial were eligible for inclusion in this study. On three occasions, 12 hours apart, during early pregnancy using a continuous measure of nausea, vomiting, and retching, women assessed the amount, duration, and severity of symptoms as they occurred. After the birth of their infants, they provided information about the duration of nausea, vomiting, and retching as well pregnancy outcome information by responding to a mailed questionnaire. Multivariate methods were used to analyze data. Results: More severe vomiting in early pregnancy was likely to continue for a longer period of time and was related to decreased infant birthweight. Gestational age, parity status, and severity of vomiting were predictors of infant birthweight and together explained 22 percent of the variance in birthweight. A significant relationship between fetal gender and severity of nausea and vomiting was not found. Conclusions: It may be possible to identify women at risk for third trimester vomiting and to provide appropriate nutritional support and counseling so that their risk of having a low-birthweight infant is reduced. A larger sample would be required to assess the relationship between fetal gender and severity of nausea, vomiting, and retching.