The absence of a fetal heartbeat for more than 40 days of pregnancy is usually a normal phenomenon. Because everyone’s menstrual cycle is different, when the menstrual cycle is longer, ovulation is later than the normal cycle and the appearance of the fetal heartbeat and germ may be later compared to the time when the gestational sac is seen in the uterus. If a woman usually has a regular menstrual cycle of 28-30 days, the fetal bud and fetal heartbeat can usually be seen by vaginal ultrasound at about 6 weeks of pregnancy (42 days), indicating that the fetus is in a viable state. If the menstrual cycle is longer, once every 30-40 days or even longer, the fetal heartbeat will be seen later, around 8-9 weeks (56-63 days) or even a little longer. Pregnant women can combine their menstrual cycle and ultrasound to determine the time period when the fetal heartbeat appears. If the menstrual cycle is regular and no fetal heartbeat is detected on ultrasound after 7 weeks (49 days) of pregnancy, it is recommended to check again in 1 week and if there is still no fetal heartbeat or fetal bud, consider the possibility of embryonic arrest. If the menstrual cycle is long and the average diameter of the 3 gestational sacs is >2.5cm after 60 days but no fetal heartbeat is seen, it is considered that the embryo has stopped developing and the next step of treatment is recommended.