Superfetation
Superfetation is a rare type of twins. It happens when an egg is only released from the ovaries once you have been pregnant. As a result, twins are not conceived at the same time. Studies have shown that superfetation would only occur 1 out of several million cases. Up to now, there have been actually no more than 10 cases all over the world. In addition to women ovulating two times in the same cycle or during pregnancy, scientists think that this type of twins may happen when a woman has a double uterus. [6]
