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Antenatal tests

Increased risk of having child with DS after having had a child with DS?

5 replies

glimmer · 14/02/2011 21:47

I have read several times, that after having had a child with DS (or other chromosomal disorder), one is at an increased risk of having another, even if the genetic disorder is 'de novo' and not inherited. When 'increased' I mean higher than other mothers in the same age range.

Can anybody explain me why this is or point me to literature or links?

Thanks.

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TubOfLard · 15/02/2011 16:25

With DS specifically, the thinking is a degeneration of the ovum over time is the issue and people don't all age in exactly the same manner.

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babylily · 15/02/2011 18:16

hi,
Our geneticist explained it very clearly but I cannot remember the exact words - we were told one DS pregnancy gave us a risk of 1:100 (excluding age associated risk), despite going on to have an unaffected pregnancy next time, our next (Edwards syndrome) pregnancy brought our future risk to 1:50. If it had been another DS pregnancy we would have been more like 1:25.

Incidentally the risks were calculated on my husband and I together (neither genetic 'carriers' of any condition) having another affected pregnancy, and on the probability that the T21 & T18 pregnancies being caused by either a dodgy sperm or a dodgy egg, so neither of us knows who is to blame as it were.

Not a straightforward answer, but I think genetics is a bit like that when it comes to non-inherited conditions.

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glimmer · 16/02/2011 22:34

Thanks for your answers. I have to admit that I don't fully understand them but I get the idea....

They gave me a recurrance risk of 1:100,
although the risk for the genetic disorder I am interested in is 1: 200 000 000, which means my risk for having a pregnancy with this condition is increased
by a factor of 2 million !!! I thought that's sort of crazy given the rarity....

But I think it's more along the lines of picking a number that's small but not non-negligible...

Babylily - so sorry you had two pregnancies
with chromosomal disorder. Life is just not fair.

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Ilovekittyelise · 18/02/2011 09:01

To be honest having been through the same ourselves, having a clear genetic screen and yet being told our inherent risk is higher because of a previous DS pregnancy, I think that the issue is probably more genetic elements to trisomies that are not yet understood.

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jellybeans · 18/02/2011 10:59

Hi I had a baby (stillborn sadly) with a de novo disorder (much rarer than downs) and I was early 20s at conception. I have 5 living children with no genetic problems and also lost another stillborn who had no problems, she was just too premature to survive. I think it is very unusual to repeat if the parents are not carriers of a disorder/translocation but it does happen rarely.

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