During an IVF transfer, one or more embryos may be transferred. Some people believe that the pregnancy rate tends to increase as the number of embryos transferred increases, so the more embryos put in the better and the higher the success rate. However, the truth is that as the number of embryos transferred increases, so does the incidence of multiple pregnancies. Multiple pregnancies can bring about a series of complications for the mother and child. Mothers with multiple pregnancies are more likely to experience pregnancy syndromes such as diabetes and high blood pressure during pregnancy, and the probability of post-partum hemorrhage is also relatively high. In addition, multiple pregnancies are more prone to problems such as preterm labor, delayed fetal development, and fetal malformations than single pregnancies. In fact, it is not difficult to understand that embryo implantation not only requires certain requirements on the environment of the woman’s uterus, but also requires sufficient nutrients and progesterone, if too many embryos are placed at the same time instead, it will increase the difficulty of implantation. The mother and child will also face more difficulties and risks during pregnancy. Faced with so many risks to the mother and child, some people believe that fetal reduction surgery can be a remedy for multiple pregnancies, and even some multiple pregnancies will undergo spontaneous reduction at an early stage, however, more scholars have found that even if multiple pregnancies are reduced and then delivered as a single fetus, the risk of neonatal low body mass and malformations is higher than that of singleton pregnancies. The resorption of the dead fetus and its appendages, as well as the cytokines and prostaglandins produced during the resorption process, may still affect the continued development of the remaining embryos. Thus multifetal reduction as a remedy after a multiple pregnancy is not the best clinical strategy to reduce or avoid risks to mother and child. Therefore, with the improvement of in vitro culture techniques, improving embryo quality and endometrial tolerance, and thereby increasing the implantation rate of embryos, the number of embryos transferred can be effectively reduced and the incidence of multiple pregnancies decreased. The practice of increasing pregnancy rates by increasing the number of embryos transferred is extremely detrimental and has been abandoned by most reproductive centers. Numerous studies have shown that reducing the number of embryos transferred to two, when sufficient good quality embryos are available, results in a better clinical pregnancy rate and significantly reduces the incidence of multiple pregnancies.