The third trimester of pregnancy before the fetal heart is generally abnormal, usually about 50 days of pregnancy will appear fetal buds and primitive heart tube beat, but if the menstrual period is particularly irregular, easy to delay for a long time if it may also be normal. 1. Normal menstruation is regular, usually about 50 days of pregnancy will appear fetal buds and primitive heart tube pulsation, if after 50 days of pregnancy has not been buds and primitive heart tube pulsation to consider the possibility of fetal arrest, it is recommended that two days later to repeat the ultrasound to determine whether there is a fetal heartbeat, if it is determined that there is no fetal heartbeat, it is necessary to terminate the pregnancy as soon as possible. 2. If the menstrual period is usually irregular and easily delayed for a long time, it may be normal to have a fetal heart in the third trimester, because sometimes, although the menstrual period is relatively long, but the fertilization is relatively late, so there may be a case of fetal heart in the third trimester. You should relax and take regular checkups to make sure that the fetus is developing normally, then you don’t need to worry. It is rare to see a fetal heartbeat in the third trimester of pregnancy, but if you have regular checkups to make sure that the fetus is developing normally, then there is no need to worry.