Weak fetal heart at 36 days of IVF transplantation may be normal, but it does not exclude the possibility of embryo underdevelopment, etc., which can be treated by regular pregnancy tests and termination of pregnancy. Since the embryo is just developing at 36 days of IVF, the weak fetal heart may be normal at this time, and the pregnant woman usually does not have abdominal pain and other uncomfortable symptoms. At this time, attention should be paid to regular pregnancy tests to observe the fetal heart condition, avoid strenuous exercise during this period, and maintain sufficient sleep. If the embryo is underdeveloped, it can also lead to the occurrence of weak fetal heart at 36 days of IVF, and the pregnant woman may experience symptoms such as vaginal bleeding. At this time, if it is caused by low progesterone, you can use follow the doctor’s advice to use progesterone capsules and other treatment, if necessary, can take the termination of pregnancy. If a pregnant woman has a weak fetal heart on the 36th day of IVF transplantation, it is recommended that she seek medical attention in a timely manner, under the guidance of the doctor, complete the relevant examinations, clarify the cause of the disease, and provide symptomatic treatment.