PURPOSE: Symptoms of nausea and vomiting are commonly experienced during early pregnancy (nausea and vomiting of pregnancy or NVP) and have been associated with stress, anxiety, and depression in pregnancy. However, nausea and vomiting in late pregnancy is a little-studied phenomenon. The purpose of our study was to examine the prevalence, severity, and psychosocial determinants of NVP during early and late pregnancy. STUDY DESIGN AND METHODS: Data were originally from a longitudinal and epidemiological study of depression in pregnancy and postpartum in a cohort of 648 Canadian women conducted from 2005 to 2008. Measures included the Nausea and Vomiting in Pregnancy Instrument (NVPI), the Cambridge Worry Scale (CWS), and the Edinburgh Postnatal Depression Scale (EPDS). Demographic, maternal/obstetrical, psychological, and behavioral variables related to NVP were also examined. Odds ratios and 95% confidence intervals were calculated for all risk factors investigated using multiple logistic regression, controlling for potential confounders. RESULTS: The prevalence of NVP was 63.3% (n = 551) at Time 1 (early pregnancy) and 45.4% (n = 575) at Time 2 (late pregnancy). Severity of symptoms was associated with earlier gestation, antiemetic medication use, employment status, and symptoms of major depression. Maternal smoking and having the support of three or more persons were protective for NVP. CLINICAL IMPLICATIONS: This study suggests that screening for NVP should be ongoing throughout pregnancy and measures that address NVP, poor social support, and depression are warranted. Further research is needed in regard to effective management of this very common and distressing condition.