Sperm enters the mother’s body 7~8 days after implantation. Sperm enter the mother’s vagina after intercourse and can survive for 2~3 days, after wandering into the fallopian tube to combine with the egg to form a fertilized egg in order to complete the fertilization process, which mostly occurs within 24 hours after ovulation. Six to seven days after fertilization, the fertilized egg develops into a late blastocyst and is implanted in the endometrium to complete implantation. Therefore, after the sperm enters the mother’s body during ovulation, the process of fertilized egg implantation can be completed in 7~8 days. The trophoblast cells begin to secrete HCG (human chorionic gonadotropin) about 1 day after the fertilized egg is deposited, and a blood HCG test is usually performed about 10 days after intercourse to confirm pregnancy, and can also be used to determine the development of the embryo based on its doubling. Ultrasound is usually performed around 40 days after menopause to confirm a normal intrauterine pregnancy.