Pregnancy does not usually occur on the fourth day of menstruation, but there is no exception for accidental ovulation.
For a woman on day 4 of her period, this is a time when the follicles are in the growth and development stage, and no mature follicles will be discharged, so pregnancy is usually not possible. However, for women with irregular menstrual cycles, this period may also be abnormal uterine bleeding, and it is possible to ovulate on the 4th day of menstruation, so pregnancy is also possible.
For women on the 4th day of menstruation, the menstruation may not be completely clean or just clean, the uterus and other organs have not yet fully recovered, at this time coitus may cause blood to flow out of the uterine cavity and a small amount of vaginal bleeding, but also increase the risk of gynecological inflammation such as vaginitis, pelvic inflammatory disease, so coitus is also not recommended at this time.
For women who do not want to have children, it is also recommended to do a good job of contraception to avoid the occurrence of unwanted pregnancies.