The fastest and accurate way to diagnose early pregnancy is to have a blood test for HCG 6-7 days after sex. After sexual intercourse, a woman’s egg and a man’s sperm unite in the fallopian tube to form a fertilized egg, which gradually settles into the uterus and forms trophoblast cells after 6-7 days. Trophoblast cells can secrete HCG, but it is only expressed in the blood in the early stage, and the concentration in urine is too low to be detected. A urine test performed 35 days after menopause can also provide a clear diagnosis of early pregnancy. In addition, an ultrasound test performed 35 days after menopause will not only clarify early pregnancy, but also rule out abnormal pregnancy conditions such as ectopic pregnancy. HCG elevation is not only seen in pregnant women, but other diseases of the female reproductive system may also cause abnormal HCG elevation, so further ultrasonography should be performed to confirm the diagnosis when HCG elevation occurs.