RE: [MLUG - DISCUSSION] Identical Twins

[Mike Miller <EMAIL:PROTECTED>]

On Tue, 4 Jan 2005, Vern Green wrote:

> My wife just had an interesting thought though. How do they know they 
> are identical? I am not doubting you at all and perhaps they have a 
> means I am not aware of, but I know myself the ultrasounds we got ten 
> years ago did not have enough detail to know. They had a hard time 
> convincing me I was going to have a son pointing at that little dot on 
> the image.

On Tue, 4 Jan 2005, Spurling, Shannon wrote:

> I think it has something to do with how the twins are implanted in the 
> womb. I think identical twins share some portion of the sack, where they 
> are all in completely separate sacks if they are paternal. I may be 
> wrong, but it seams that is how it would work since identical twins are 
> from a separation of the same egg...


That's nearly right.  This page has good information:

http://www.parentsplace.com/pregnancy/labor/articles/0,,166530_111532,00.html

The thing that people sometimes get wrong is they believe that "identical" 
(monozygotic or MZ) twins must be monochorionic (sharing a placenta), but 
they can be dichorionic.  It works perfectly in the other direction - all 
monochorionic twins are MZ.  So Nathan's doctor can predict that the twins 
are monozygotic if they are monochorionic.

Mike
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