The yolk sac is an indication of normal embryonic development and can be detected during an ultrasound examination at 6 weeks of gestation. The yolk sac shrinks with each week of pregnancy and disappears at around 12 weeks of pregnancy. If the yolk sac is not visible on ultrasound after 7 weeks of pregnancy, it may be an empty gestational sac, which is not a normal pregnancy and there is a risk of embryonic arrest. If you see the yolk sac and the fetal heart and germ at around 8 weeks of pregnancy, it means that the embryo is developing normally. If the ultrasound examination is normal, you should usually pay attention to rest, avoid strenuous exercise, no sexual intercourse for three months, and if you have stomach pain or vaginal bleeding throughout the pregnancy, you must go to the hospital for examination in time.