	How many multiples are there?
	What causes multiples?
	Identical or not?
		Ways of determining zygosity
		Common misconceptions about zygosity
		Not all MZ twins are identical - the twin-twin transfusion syndrome
		Does it matter?
		Using the Zygosity Questionnaire
		Download the Zygosity Questionnaire (word format 32k)
	Starting life as a multiple
	What would you do?
	References

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Common misconceptions about zygosity

The most common myth is that only DZ twins have separate placentas. Firstly many DZ twins may have fused placentas that cannot be distinguished in the rush of the delivery room after the arrival of multiples. More significantly, there are a significant number of MZ twins who have separate placentas. The old myth about one placenta = identical twins still persists. Where there are separate placentas, the babies will be separated by two membranes, the inner amnion and the outer chorion. While an experienced ultrasonographer will be able to identify the number of membranes around the unborn multiples, we have all heard stories like

"He said they were going to be identical and that's what we told everyone. It took a bit of explaining when Alison and Peter were born!"

Disclaimer:
Information on this site is based on extensive studies of multiples in schools. However it may not apply to the specific circumstances of an individual family and the authors accept no liability for the way in which the information is used.

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