If you have vomiting symptoms when your period comes, to rule out the possibility of conception, you can usually take a pregnancy test 12 days after intercourse to rule out conception, without waiting for your period to be delayed. If it is determined that there is no conception, there are more reasons for vomiting: 1. Before the menstrual period, the body progesterone and persistent increase, due to changes in hormone levels, will also cause confusion in the gastrointestinal tract function, and will cause the symptoms of vomiting. It can also be caused by the withdrawal of progesterone 1-2 days before the menstruation. 2. When eating spicy and stimulating food, including raw and hard food or even cold stomach, it may cause the symptoms of vomiting. 3. When there is indigestion or stimulation caused by excessive release of prostaglandins in the body, it can also cause the symptoms of vomiting, which will subside after the end of the menstruation. It will not affect the health of the body.