A yolk sac is usually present about 1 week after the presence of a gestational sac, but there can be individual variations. In early pregnancy, an intrauterine gestational sac can usually be seen on ultrasound at about 35 days after menopause, suggesting a normal intrauterine pregnancy. The yolk sac is the round, sac-like structure next to the embryo bud and is usually present about a week after the presence of the gestational sac. When the ultrasound during early pregnancy suggests that the yolk sac is clear and of normal size, it can be inferred that the embryo is well developed. The normal diameter of the yolk sac ranges from 3-8mm, when the yolk sac diameter >10mm or the yolk sac does not show, deformation or internal strong echoes and other changes are mostly suggestive of a poor prognosis. Combined with progesterone, blood HCG (human chorionic gonadotropin) measurement value is low can be diagnosed. Progesterone, heparin and other medications should be given to preserve the fetus, and the pregnancy should be reviewed on a regular basis, and if necessary, terminated.