The fetal heart is usually present 1-2 weeks after the appearance of the yolk sac. Usually the fetal heart can be seen 1-2 weeks after the yolk sac is seen on ultrasound, but the time when the fetal heart can be seen varies depending on whether the woman has regular menstrual periods or not. If a pregnant woman’s menstrual period usually comes in 28~30 days, the gestational sac and yolk sac can be seen in the uterine cavity by ultrasound 4~5 weeks after menopause. About 1 week after the appearance of the yolk sac, ultrasound can see fetal buds and primitive heart tube pulsation, and the rhythmic beating of the fetal heart can be seen in the fetal buds, which is an early and important sign of the survival of the embryo. If a pregnant woman has irregular menstrual periods before pregnancy, ovulation may be delayed, and the formation of the fetal heart and buds will also be delayed. Usually, the fetal heart and buds can be seen around 1~2 weeks after the appearance of the yolk sac. However, it should be noted that if the yolk sac appears for 10~14 days and still no fetal buds are observed, there is a possibility that the embryo is in diapause, which can be continued to be observed for another 1 week, and if the fetal heart and buds still can not be seen, it is necessary to be handled under the guidance of a professional physician.