Generally the embryo is easy to implant when estradiol is ≥300pg/mL, and pregnancy can be determined by testing blood HCG levels. Fertilization occurs within 24 hours after ovulation, and the embryo will be implanted in the uterine lining 6 to 7 days after fertilization. One of the necessary conditions for embryo implantation is the presence of adequate amounts of estrogen and progesterone in the body, which can support the endometrium to be tolerant and more conducive to embryo implantation, and the embryo can easily implant when estradiol levels are ≥300 pg/mL. Generally, HCG (human chorionic gonadotropin) starts to be secreted 1 day after embryo implantation, so blood HCG test can be performed about 10 days after ovulation under the guidance of doctor to confirm pregnancy. An ultrasound should also be performed at about 6 weeks after menopause to confirm a normal intrauterine pregnancy. When abdominal pain and vaginal bleeding occur, you need to go to the hospital promptly.