There is no specific value for the probability of success in fetal heartbeat preservation, but the chances of success through fetal preservation are still very high. The weak fetal heartbeat is usually caused by a small gestational week at the time of examination, or low progesterone or poor development of the embryo itself. 1. Smaller gestational week at the time of examination: the probability of success in preserving the fetus at this time is very high. Because the gestational week is small, the embryo development time is still short, the fetal heartbeat is relatively weak, later with the prolongation of the embryo development time, the fetal heartbeat will be gradually strengthened, which is a very normal development process. 2. Low progesterone: If low progesterone causes weak fetal heartbeat, then progesterone drugs can be used to protect the fetus is mostly successful. 3. Poor development of the embryo itself: the chances of fertility preservation in this case are smaller. This is because if the embryo continues to develop poorly at a later stage, even if the fetal heart appears, it may encounter fetal arrest in the process of development. The safest way to preserve the fetus is to monitor the development of the embryo through clinical ultrasound, so that the doctor can give the corresponding measures to preserve the fetus, so that the probability of successful preservation of the fetus is still very high. During the period of fetal preservation, pregnant women should also pay attention to rest, maintain a stable state of mind, avoid emotional fluctuations, and actively cooperate with the doctor to carry out the treatment of fetal preservation.