TWINS - 365 Days of Twinipedia: Day #113

Day One-Hundred and thirteen of Twinipedia 

Fact #113

When twin eggs implant close to one another in the mother's womb, the placentas can actually become so close and attached that they fuse together, forming what appears to be one placenta.

This occurrence is one of the reasons why it is tricky for doctors to only look at the placenta as a way to determine if a set of twins are from one egg that split (monozygotic) or from two eggs that were produced separately and then each fertilized (dizygotic).


Twins can end up being mislabeled as monozygotic (from one egg that split) if this method is used since the impression given by the one placenta is that only one egg was ever produced in the beginning, thus the one placenta.  
Too interesting to us!