The reasons for not seeing primitive heart tube pulsation include late embryo implantation, poor embryo development or pregnancy cessation. 1. Late implantation of embryo: Usually, primitive heartbeat can be seen around 7 weeks of pregnancy after the formation of the gestational sac. If the fertilized egg of a pregnant woman is formed at a later time, and the gestational period is shorter, the embryo develops small, and the examination is too early, the primitive heartbeat may not be seen, which belongs to the normal phenomenon, and it can be detected again at 9 weeks of pregnancy to detect whether there is a primitive heartbeat or not. 2. Embryonic dysplasia or termination of pregnancy: If there is still no primitive heartbeat after 9 weeks of pregnancy, it may be due to various reasons, such as insufficient nutritional intake, environmental factors, etc., resulting in embryonic dysplasia or termination of pregnancy, which may lead to the symptoms of not seeing primitive heartbeat. When the clinical manifestation of no primitive heartbeat occurs, pregnant women should go to the hospital in time for further examination and treatment under professional doctor’s treatment.