If the male partner’s semen is normal and the female partner is in ovulation, the fertilized egg usually settles in about 7 days after intercourse. The fertilized egg is usually formed within 24 hours after intercourse, the early blastocyst enters the uterine cavity 4 days after fertilization, the late blastocyst is formed 5-6 days after fertilization, and the late blastocyst implants into the endometrium 6-7 days after fertilization, i.e. the fertilized egg is implanted. Successful implantation must include disappearance of zona pellucida; differentiation of blastocyst trophoblast out of syncytial trophoblast; synchronized and coordinated development of blastocyst and endometrium; and sufficient estrogen and progesterone, requiring luteal secretion of estrogen and progesterone. After the fertilized egg implants in the endometrium, some women may experience a small amount of implantation bleeding, which usually does not require treatment. The level of human chorionic gonadotropin rises rapidly after pregnancy, so pregnancy can be confirmed by a blood test for hCG on day 7.