What are twins? Twins refer to two mature embryos in the same pregnancy. Generally, twins are either identical twins or fraternal twins. Identical twins are two fetuses from the same fertilized egg that split into two embryos shortly after fertilization; fraternal twins are two eggs from the mother fertilized by two sperms. Signs of twin pregnancy According to statistics, the occurrence rate of twins is about 1/80. If you suspect that you are pregnant with twins, here are some signs for your reference: 1. Feelings early in pregnancy