After IVF transplantation, the role of intramuscular injection of progesterone is mainly in the following two aspects: 1. Supplemental progesterone to promote the growth and development of the fetus. IVF is not a natural conception, the hormone level changes in the female body and the growth and development needs of the fetus, is not absolutely balanced, there is a tendency to be a relative shortage of hormones, so it is necessary to supplement the progesterone to promote the development of the fetus.2. Progesterone is able to reduce the sensitivity of the uterus, inhibit uterine contraction, and is able to increase the success of embryo implantation, and to play a role in preservation of the fetus. Fertilized eggs are formed by combining sperm and egg. Sperm is provided by men and is a foreign substance to women. Therefore, in some cases, the fertilized egg will easily cause uterine contractions during implantation, resulting in failure of implantation or miscarriage. The use of progesterone can inhibit uterine contractions and increase the success rate of IVF.