In vitro fertilization is a way to achieve conception by forming fertilized eggs in vitro and transplanting them into the uterine cavity. The reference range of HCG value at 11 days after transfer is around 100 mlU/ml. 11 days is equivalent to one month of pregnancy for women. If the HCG is checked by blood test and found to be lower than 100 mlU/ml, further examination is needed to indicate the presence of poor embryonic development. If the HCG doubling is found to be normal, you can continue to observe and take fetal preservation treatment, because the HCG doubling indicates that the fetal development is just slower than normal, and you can take progesterone or inject progesterone to replenish the progesterone and HCG needed in your body for fetal preservation treatment under the guidance of your doctor. The first thing you need to do is to avoid having sex during the post-transplant period and pay more attention to a balanced diet and keep warm.