Is it possible not to hear heart beat in the womb?

Yes, it is possible not to hear a heartbeat in the womb during the first few weeks of pregnancy. This is because the embryo's heart is still very small and the fetal heartbeat is often too faint to be detected by a Doppler ultrasound. In general, a fetal heartbeat can usually be detected by transvaginal ultrasound as early as 5-6 weeks of gestation and by abdominal ultrasound by 8-12 weeks of gestation. However, there are certain factors that can affect the ability to hear a fetal heartbeat, such as the position of the fetus, the amount of amniotic fluid, and the sensitivity of the ultrasound equipment. If a heartbeat cannot be detected, it does not necessarily mean that there is a problem with the pregnancy, and further tests may be needed to determine the cause and monitor the pregnancy's progress.