Usually there is no gestational sac in the 3rd week of pregnancy, and the sac usually appears around the 5th week of pregnancy, with the fetal heart and buds appearing around 1-2 weeks after the appearance of the sac. The gestational sac is the original placental tissue, the first form of pregnancy, and will only be present in the early stages of a woman’s pregnancy, usually disappearing by the 11th week of pregnancy. The sac is detected during an ultrasound and the location and area of the sac is used to determine whether the pregnancy is intrauterine or extrauterine. When there is an empty gestational sac, no buds and no heart, it means that the development of the embryo is abnormal. When the gestational sac is irregular, blurred and accompanied by vaginal bleeding, the pregnancy needs to be terminated. Sometimes the gestational sac may be small, the small size of the gestational sac may be related to the late time of conception, and does not completely mean that the fetus is not well developed. As long as the development of the embryo is normal, there is no need to worry. If the size of the gestational sac does not correspond to the gestational week, it is recommended to do an ultrasound to observe whether the fetal heart and buds are developing normally, and pay attention to regular visits to the hospital to check the development of the fetus.