Generally, the yolk sac, fetal bud echoes and primitive heart tube beats are visible at 6~7 weeks of pregnancy, and the fetal bud is about 0.3cm long. In most women, the yolk sac and the embryonic buds are first seen by ultrasound at around 6 to 7 weeks of pregnancy, and the embryonic buds of 0.3cm can be seen at around 45 days of pregnancy, at which time the primitive heart tube pulsation is visible. Some women usually have a longer menstrual cycle, and the fertilized egg will be deposited later, so the appearance of the yolk sac, embryo buds and fetal heart may be delayed, and the primitive heartbeat will not be visible at 8 weeks of pregnancy, so you can delay it for 1 week and go to the hospital for a check-up. Some women have empty sac pregnancy after pregnancy, through the ultrasound examination has not been able to see the yolk sac, fetal buds, fetal heart development, this situation is abnormal phenomenon, may be the embryo chromosome abnormality, maternal physical disease caused by, to go to the examination to confirm the diagnosis of timely termination of pregnancy. If abdominal pain, vaginal bleeding and other abnormalities occur in the early stages of pregnancy, you should consult a doctor promptly.