The chances of pregnancy are relatively small if you have intercourse 3 days after your period. 3-5 days after menstruation, 3-5 days before menstruation is a relatively safe period, called the safe period, the safe period and the dangerous period is also the ovulation period relative to each other. Ovulation is the 14 days before the next menstrual period, around a week before and after this time to properly increase the opportunity to have intercourse, the chances of pregnancy will increase, but the safe period contraception is not safe. If there is no requirement to have children in the short term, it is recommended to use external condoms or oral contraceptives. In addition to the main influence of the hypothalamic-pituitary-ovarian axis, menstruation and ovulation are also related to other external factors, including emotional changes, geographical changes, climate changes, significant weight gain or loss in a short period of time, and so on, which may affect normal menstruation and the timing of ovulation.