The lack of a yolk sac after a successful IVF transfer can be caused by a shorter number of days of pregnancy or a poorly developed embryo. If you have had the transfer for less than a month and there is no yolk sac, you usually don’t need to worry too much. Because of the short days of pregnancy, it is normal to not see the yolk sac for a while. A week after the interval and then do ultrasound review, by doing review, generally more than 1 month after transplantation can normally see the original heart tube fluctuations and yolk sac. If you have done the transfer for more than one month, you still can’t see the yolk sac, and the diameter of the gestational sac is smaller than the normal range, and the shape of the gestational sac is irregular, it may be caused by the poor quality of the embryo, the embryo stops developing, etc., and you need to do further checkups, and take appropriate measures according to the situation in a timely manner. After successful in vitro fertilization, you should follow the doctor’s instructions for timely follow-up examination, and actively deal with any abnormalities.