A blood test one month after coitus can detect pregnancy, but there are individual variations. For women with reproductive requirements, pregnancy can mostly be confirmed when the blood hCG level is checked one month after intercourse. Generally, one week after intercourse, the trophoblast layer of the fertilized egg secretes HCG, and at this time, blood can be drawn to test for HCG to determine whether or not you are pregnant. If the HCG level in the blood is elevated, it means that you are pregnant. Therefore, pregnancy can usually be detected one month after intercourse. For women with long menstrual cycles, pregnancy may not be detected at this time either. However, when pregnancy is not clear, you need to follow the doctor’s instructions for dynamic observation, and review the blood hCG and ultrasound and other related examinations. When abdominal pain, vaginal bleeding and other abnormalities occur, you need to go to the hospital in time.