Friday, 29 July 2011

Are they or aren't they?



I wanted to find out once and for all whether the boys are identical. They are getting more and more similar, and a few of the signs make us wonder. Of course they have the same colour hair and eyes, and so far all their teeth have come through in the same order.  They weigh nearly the same, and they have no physical features that distinguish one from the other except for Felix's double crown.


Here's a little lesson on zygosity.

  1. One placenta - must be monozygotic (identical) 
  2. Two placentae - could be monozygotic (identical) or dizygotic (fraternal). If the egg has split early, before the placenta starts to form, then they could be identical. This occurs in about one third of identical twins.
Well, it's a bit more complicated than that, but that's the simplified version.

So the boys had a placenta each (I should know, I had to deliver them), which means they are probably fraternal, but there's a small chance they are identical. Anyway, I contacted (through the Multiple Births Foundation) a KCL lab which runs zygosity tests based on samples taken from cheek swabs.

I spent ages researching various alternative labs, which have widely varying prices. In the end we chose this one, since there's some information on the site about how they conduct the test, what the chances are of the results being incorrect etc. Also KCL seems pretty respectable, and the test is done at cost (80GBP) because, I guess, they can use the information they collect for further study. It's quite funny looking for zygosity tests, because they are usually offered by labs which specialise in paternity testing, so anyone checking my Chrome history would find paternitytest4u.com, whosthedaddy.co.uk and so on. Ok I made the second one up, but you get the picture. 

We sent off the swabs last Tuesday, they were received this Tuesday, and the results should be available on Monday! Exciting. Jo asked me if I'd be disappointed if they weren't identical - it would be cool if they were, but if they're not that just confirms their individuality so that's cool too. 

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