Contraceptive pills taken by women, which have the effect of preventing the fertilization of egg cells, are useful after ovulation. After the organism has ovulated, taking birth control pills can interfere with the combination of sperm and egg. So even if a woman takes the pill after ovulation, she can still achieve contraception. Women with a family history of venous thrombosis are cautioned to use birth control pills with caution. Women with a history of venous thrombosis are prohibited from using it. Adverse reactions such as abdominal pain and depression may occur when using birth control pills, and care should be taken to use them under medical supervision. Although taking birth control pills after ovulation is useful, the possibility of pregnancy still exists. If a woman of childbearing age has recently had sex and experiences delayed menstruation, she should actively visit the hospital to check for pregnancy.