The presence of a yolk sac does not necessarily mean that the embryo is well developed. If the embryo is well developed, the yolk sac should be between 3-8mm. If it is more than 8mm or less than 3mm, it means that the embryo is not developing well and it is possible that the embryo has stopped developing. Under normal circumstances, if you see the yolk sac in the uterine cavity, you must see the fetal heart and buds after another 11 days. If you can’t see the fetal heart and buds for more than 11 days, it means that the embryo has stopped developing, and you need to have an abortion as soon as possible, which may cause uterine infections or heavy bleeding after a long period of time.