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Are they identical 1 placentas or 2 placentas fraternal?" This is probably the most common question asked of parents of multiples. Many people do not understand what they are really asking, assuming that it is just a matter of twins having similar physical appearance. But twin type is actually determined long before the twins are born. The terms identical and fraternal are common words that refer to zygosity -- the characteristics of the cell union that happened at conception.

There are exceptions:
http://multiples.about.com/cs/funfacts/a/twinzygosity.htm

13 years ago. Rating: 1
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