Pregnancy detected on the 4th day of intercourse can basically be concluded that it is not caused by this intercourse, but by the previous intercourse. Even if you have intercourse on the day of ovulation, the average time for a fertilized egg to enter the uterine cavity and to be fertilized is 6-7 days. The average time from intercourse to clinical fertilization of the fertilized egg is 7-10 days, and pregnancy may be detected only after the fertilized egg is fertilized. There are many methods of pregnancy testing, the most convenient one is the early pregnancy test, but this test can only be tested 10-14 days after fertilization and it may be inaccurate, so it is not used as a confirmatory method. The fastest and most reliable method is the blood test, which uses the value of the human chorionic gonadotropin secreted in the woman’s body after the formation of the fertilized egg to determine the pregnancy. This hormone is not secreted until the 6th or 7th day after fertilization, so the pregnancy test is usually performed about 7 days after intercourse. After pregnancy is detected, it is necessary to have regular maternity checkups, do a good job of fetal preservation treatment, and pay attention to keeping your mood calm and relaxed, so as not to have excessive psychological burdens.