If your menstrual cycle is relatively regular, you can determine whether you are pregnant through blood HCG test about 10 days after intercourse during ovulation. Under normal circumstances, human chorionic gonadotropin, or HCG, usually begins to secrete rapidly 6 days after fertilization, and can be detected in the blood about 10 days after intercourse, which is also a commonly used method of detecting early pregnancy in clinical practice. However, the value of blood HCG at this time will be relatively low, about 50-200U/L, but still higher than the level of non-pregnancy. Therefore, about 10 days after intercourse, you can go to the gynecologist to determine whether you are pregnant through blood HCG test. In addition, urine HCG test and ultrasound can also determine whether you are pregnant or not, but both of them are not as early and accurate as blood HCG test. HCG can only be detected in urine after a certain concentration of HCG in the blood, and ultrasound can only detect the pregnancy sac in the uterine cavity 3 weeks after coitus, that is, about 1 week after the menstrual period has been delayed.