It is not possible to get pregnant if you have intercourse during the physiological period, because it is not yet time to ovulate. During the ovulation period, the egg can only survive for 24 hours if it is not fertilized. However, it is recommended not to have intercourse during the physiological period, because the vaginal bleeding is caused by the shedding of the endometrium of the uterus, so when the endometrium is not yet repaired and the vagina is still bleeding, intercourse may lead to the introduction of pathogenic bacteria into the uterine cavity, causing inflammation of the endometrium. In addition, the stimulation of intercourse may cause contraction of the uterus, which may cause menstrual blood to flow backwards down the fallopian tubes and into the pelvic cavity, which may result in endometriosis. Clinically, endometriosis not only causes menstrual pain, but also causes infertility.