Under normal circumstances, the first time after intercourse will not lead to delayed menstruation, but menstruation is affected by mental factors, nutritional factors, life and study pressure, specifically the following: 1, if excessive mental tension, often stay up late, sudden changes in the living environment, easy to cause delayed menstruation. 2, if the first time after intercourse mental stress, may lead to delayed menstruation, it is best to observe to see the menstrual flow. The first time you have intercourse is during ovulation, if you don’t take contraceptive measures, you may get pregnant and have a delayed period. 4. If you don’t pay attention to your vulva hygiene during intercourse, you may bring bacteria or virus into your vagina, which may cause vaginitis and pelvic inflammatory disease, which may also cause a delayed period. Therefore, if you have delayed menstruation after the first intercourse, you need to have early pregnancy check, routine white belt check and gynecological ultrasound check to identify the causes and then treat them reasonably.