Saturday, March 6, 2004

The soon to bes in view

Often it seems that even the brightest news must be slightly clouded over. Yesterday, we learned that Mrs Zen is carrying one of each sex.
Of course, I am very pleased that I will have another daughter, but I am in many ways a typical man, and the idea of having a son is thrilling. I suppose that the idea that you will improve on your father's life -- better him in your achievements in all spheres -- however stupid an idea that might be, however irrational you know it is, does drive men a little.
I don't know whether women ever feel that way.
But there is a very small but potentially very dark cloud. Both XX and XY, as they are known, have choroid plexus cysts, something I had never heard of before yesterday, and something I wish I had never had to find out about. In one case, the cyst is quite large.
These cysts are, in nearly every case, a simple developmental quirk. They occur in one in a hundred fetuses. They disappear after a few weeks, and have no ramifications. However, where there are no other markers, they mark for trisomy 18 in one in a hundred cases. The sonographer searched very hard for other markers, and found none -- no club foot, no clenched fist, no heart problem. So there really is nothing to worry about.
Except, if it's a one in a hundred chance, it is 10,000 to one that both babies just happen to have it (because they are dizygotic and are no more the same than two separate fetuses). That worries me. There are I think three possible answers:
1/ It is pure chance and the twins really are one in 10,000. I am too much the rationalist to believe that.
2/ It is caused by something genetic, and either I or Mrs Zen has this thing (it is found in normal people, who show absolutely no symptoms of having it). Zenella might have had it undetected. So both might have inherited the allele responsible. I haven't found anything to suggest a genetic cause though.
3/ A corollary of number 2, I suppose. The twins are actually what is called polar twins, and share half their genetic material (without going into it, twins can be from one egg but fertilised by two sperm). This would mean they are more closely related than fraternal twins normally are -- the two sperm can obviously be X and Y, so they can still be different sexes. This is what I fear.

The sonographer and the consultant obstetrician who looked through the sonographs felt it was nothing to worry about, but I wonder whether it simply didn't occur to them how rare it would be to find two babies together with the condition. The sonographer, if she scanned three sets of twins a day (which she might, because she is the twins specialist), would have to work for 15 years before seeing it again.

Of course, this is a very minor thing. It makes me feel immense sympathy for those parents who are presented with the news that there are other markers -- that their child, whom they had already begun to love (even if like me, they do not believe that a foetus is alive, well, we love the potential, the idea, the dream), will be ruined. This is a very unlikely outcome for me -- the young Zens are whole, with fast-beating, strong hearts, and I wholeheartedly believe they will be beautiful children.


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