A recent prospective study of 363 pregnant women found that 20% had no symptoms of nausea and vomiting, 28% just feel sick, and 52% feel sick and vomited. Symptoms peak at about the ninth week of pregnancy and often stop suddenly by about the 14th week. Two-thirds of women will have similar symptoms in successive pregnancies. Extrapolating from this study, it is likely that 8.5 million working days per year are lost because of pregnancy, nausea and vomiting. "Epsiodic daytime pregnancy sickness" is a more accurate term than "morning sickness" for this condition.