The incidence of multiple births by natural conception is only 1%, and the incidence of multiple births by IVF is as high as 30%. Why is the rate of multiple births so high with IVF technology? The main reason is that 2-3 embryos are often transferred during the embryo transfer process to ensure success. Multiple births occur when all the transferred embryos are implanted. Therefore, it is mainly the increase in the number of transferred embryos that leads to the occurrence of multiple births. It should be emphasized that miscarriage, preterm delivery and neonatal complications are significantly increased in multiple births and therefore multiple births should be avoided as much as possible.