Vomiting during menstruation is not necessarily a sign of pregnancy. This is due to the fact that menstrual blood contains a certain amount of prostaglandins, which can enter the blood circulation and cause smooth muscle contractions in the gastrointestinal tract, leading to nausea and vomiting. Some women have relatively high levels of prostaglandins in their menstrual blood and the symptoms of nausea and vomiting are more pronounced. Vomiting in pregnancy usually occurs around 6 weeks after menopause and is often more common in the morning. Pregnancy cannot be determined by the symptoms of vomiting, but can be clearly diagnosed by urine pregnancy test or blood HCG test. If pregnancy is ruled out and vomiting occurs during menstruation, eat a light diet with small, frequent meals and avoid greasy, cold, spicy and irritating foods.