The absence of a yolk sac at six weeks of pregnancy is not necessarily hyperemesis gravidarum, but should be judged in conjunction with the ultrasound examination. Early pregnancy should follow the doctor’s instructions in the menopause about 5 weeks of ultrasound can be seen in the uterine cavity of the gestational sac and yolk sac, and clear intrauterine pregnancy, six weeks of pregnancy ultrasound can be seen in the fetal buds and fetal heart. However, if there is no yolk sac in the ultrasound examination at 6 weeks of pregnancy, it may be caused by the long menstrual cycle and late ovulation, which makes the pregnancy short, or the embryo is not well developed, and it is not necessarily hyperemesis gravidarum, so it can be rechecked according to the doctor’s advice. Gestational trophoblastic disease is a kind of pregnancy, ultrasound examination of the uterine cavity, no gestational sac or fetal heart, filled with uneven dense or short stripes of echoes, may be in the form of snow or honeycomb, combined with the blood HCG (human chorionic gonadotropin) level is abnormally high can assist in the diagnosis. Once the diagnosis is clear, the uterus should be removed and the patient should be followed up regularly after the operation. In the absence of a yolk sac at six weeks of pregnancy, a follow-up examination is required to clarify the cause of the absence of a yolk sac, and the cause of the absence of a yolk sac should be addressed.