The yolk sac disappears and cannot grow back. After pregnancy embryo in the uterine cavity bed and development, generally in the menopause 5-6 weeks through ultrasound will see the yolk sac, suggesting that the embryo is active, yolk sac appears 1 week after the appearance of the fetal heart, suggesting that the fetus is viable, you can go on with a normal pregnancy. After pregnancy through ultrasound examination of the yolk sac disappears, it is recommended to change the examination equipment and examination of the doctor to review again, suggesting that the disappearance of the yolk sac indicates that the embryo stops developing, the yolk sac will not grow back, the yolk sac atrophy after the death of the embryo is gradually being absorbed, to terminate the pregnancy in a timely manner to deal with the prolonged retention of the coagulation dysfunction and other complications may be caused. Early pregnancy should do a good job of pregnancy checkups, found that the yolk sac disappeared do not wait for its regrowth, to seek medical attention in a timely manner.