If no fetal bud is seen on ultrasound, the possible reasons include short days of pregnancy and embryonic arrest, as follows: 1. Short days of pregnancy: for women with regular menstrual cycle and around 28 days, the gestational sac can be detected by ultrasound about 5 weeks after menopause, while the development of fetal bud and fetal heart needs to be about 6 weeks after menopause. If the days of pregnancy are short and the fetal bud has not yet developed, the fetal bud cannot be observed on ultrasound, and there may be a case of amenorrhea first and pregnancy later. If the menstrual cycle is often delayed, the time to see the fetal bud on ultrasound should be postponed, and the specific time is related to ovulation, which can be judged according to the results of blood sampling; 2. Embryo stop developing: usually the fetal sac can be observed on ultrasound between 6-7 weeks of pregnancy, if the fetal sac has been detected for 2 weeks or more and still no fetal bud appears, or the length of the fetal bud is more than 5mm and still no fetal heart is seen, it should be If the embryo has not appeared after 2 weeks or more, or if the length of the germ is greater than 5 mm and no heart is seen, the embryo should be considered to have stopped developing. The common causes of embryonic arrest are chromosomal abnormalities of the embryo, medication and pregnancy-related diseases. For both of these reasons, if the pregnancy is short, it is recommended to wait for 1-2 weeks before reviewing the ultrasound to see if the fetal buds and fetal heartbeats appear. For suspected abnormal embryo development, it is recommended to review the ultrasound after 5 days. In addition, pregnant women should also visit the hospital for progesterone test and chorionic gonadotropin level test, and treat the symptoms according to the test results.