Pregnancy can be detected as early as 7-10 days after sexual intercourse. Under normal circumstances, after the egg and sperm have united to form a fertilized egg, it takes 6 days for the fertilized egg to settle and after it settles, it secretes human chorionic gonadotropin, or HCG, which can be detected in the blood 1 day after it settles and can be detected as early as 21-24 days after pregnancy. The time of detection varies from person to person, as early or late ovulation can occur. It is more accurate to perform the test after 35 days of pregnancy, that is, if the urine or blood test is performed more than 5 days after the menstrual period is delayed, the positive rate will be higher. Blood tests are earlier and more accurate than urine tests, and early in pregnancy, blood HCG appears to double every other day. Through blood HCG monitoring, the development of the embryo and whether the pregnancy is ectopic can be roughly determined.