Normally, twins have two separate di- being a numerical prefix for two chorions and amniotic sacs , termed Dichorionic-Diamniotic or "DiDi". However, they fuse together and appears to be a single placenta. Archived from the original PDF on Monozygotic twins who share a placenta can develop twin-to-twin transfusion syndrome. Most conjoined twins are now evaluated for surgery to attempt to separate them into separate functional bodies. Another abnormality that can result in monozygotic twins of different sexes is if the egg is fertilized by a male sperm but during cell division only the X chromosome is duplicated.
Archived from the original on 17 January
Have you heard of these rare and unique twin types?