Background. Nausea with or without vomiting of pregnancy (NVP) is the most common medical condition in pregnancy. NVP, even with mild symptoms, is associated with costs to society, patients and the health care system.Methods. A cost of illness study was performed to estimate the cost per woman-week associated with the onset of NVP in Canada, stratified according to the severity of NVP. Data were collected from 139 pregnant women, who called the Motherisk Program at the Hospital for Sick Children in Toronto.Conclusion. Nausea and vomiting of pregnancy in Canada is associated with substantial costs to society, patients, and the Ministry of Health and Long Term Care.Results. From the perspective of society, the total cost per woman-week was $124, $334 and $610 for women with mild, moderate and severe NVP, respectively. Costs from all perspectives increased with increasing severity of NVP.