Fertilization occurs within 48 hours of ovulation, the entire fertilization process takes about 24 hours, 6-7 days after fertilization fertilized egg implanted in the uterine lining is called bedding, so theoretically the earliest 7 days after intercourse, fertilized egg implanted in the uterine lining into the uterine cavity, but due to the thickening of the uterine lining of the cover, at this time ultrasound can not be seen within the uterus of the gestational sac structure. If the regular menstrual cycle of 28 days, 3 weeks after coitus, that is, 5 weeks after menopause, negative test ultrasound can see the intrauterine gestational sac to determine the early pregnancy in the uterus, 7 weeks or so to see the fetal heart buds to prove that the embryo is alive, so in the absence of bleeding and abdominal pain after pregnancy and physical discomfort, you can check ultrasound to see the development of the embryo in the 7 weeks after menopause, see the fetal heart buds after a regular obstetric examination, during the period of time, if there is bleeding and abdominal pain, the need to If you have bleeding and abdominal pain during the period, you need to consult the doctor for ultrasound examination at any time to check the condition of the uterine adnexa and the pelvis to rule out ectopic pregnancy.