The third day of menstruation is not allowed to have intercourse, for most women, the third day of menstruation is more menstrual flow, the cervical opening is very loose, this time intercourse is very easy to cause infection. After the patient’s vagina is flushed with menstrual blood, the vaginal environment will be damaged, the resistance of the vagina is very low, and the patient’s blood is the best petri dish for bacteria, so it is especially easy to cause vaginal infection during coitus, and the patient’s cervical opening is very loose, the infection is easy to pass through the vagina, the cervix into the patient’s uterine cavity, resulting in the patient’s uterine cavity infection. Uterine infection will not only lead to abdominal pain and discomfort, but also affect the patient’s uterine lining and fallopian tube mucosa, which can easily lead to secondary infertility, so the patient’s body damage is relatively large.