The first day of menstruation is the first day of intercourse, the chances of pregnancy are very small, because the ovulation period and the endometrial lining is thin and should not be placed on the bed. 1. Thin endometrial lining is not suitable for the bed: just after the end of menstruation, ultrasound often endometrial lining is linear echoes, thickness is very thin, endometrial lining is very thin, usually can’t accommodate the fertilization of the egg to the bed. 2. not to the ovulation: in addition to the end of menstruation, not to the ovulation, there is no ovulation occurs, and there is no ovulation will not be pregnant, so the end of menstruation just one day when the intercourse will not be pregnant. However, it is recommended that women have intercourse after menstruation, and it is best to wait until 2~3 days after menstruation is clean. Because the vagina is an open environment and blood is the culture medium, if you have intercourse too early it will increase the risk of reproductive tract infection. If you have any other questions, it is recommended to consult a professional doctor for guidance.