There is a chance of pregnancy if you have intercourse on the fourth day after your period is clean. If a woman’s menstrual cycle is relatively short, twenty-one or twenty-two days or so, and the menstrual period is longer than seven days or so, four days after the menstrual period has been cleaned up belongs to the woman’s ovulation period. If you don’t do a good job of contraception at this time, the chances of pregnancy are very high, and it is recommended that patients choose to take emergency contraceptive pills or choose to place a birth control ring in the uterus to reduce the chances of pregnancy. If the patient’s menstrual cycle is relatively long, about forty days, and the menstrual period is relatively short, about five days, the fourth day after the menstrual period is a safe period. If you have intercourse during this time, the chance of pregnancy is very low, but pregnancy cannot be completely ruled out. Because female ovulation is affected by many factors, ovulation disorders can occur, and ovulation can occur during the safe period. It is generally recommended that patients use contraception at all times as long as they do not intend to become pregnant.