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Standard Resolution CVS tests wont necessarily detect absolutely every chromosonal defect.

(56 Posts)
Merlot Thu 23-Jun-05 22:12:29

Oh my gosh - I hope I dont upset anyone with this post, because its really not my intention but Thomcat's post has rekindled some bad memories for me and I just feel that I need to post this:

Firstly, Thomcat I am so very thrilled that your little one has not got DS - it is truly great news and I am really pleased for you. Your baby, if born on the 22nd will be in good company as its my birthday!....and that of Noel Edomonds!!!

However, I do feel that there may be some people reading your recent posts who might be feeling that CVS is the absolutely definitive way of finding out whether there is anything at all genetically wrong with their baby and I just felt that I needed to tell people my own story.

My husband has a sister with learning difficulties and he himself has a balanced translocation (a chromosonal anomaly which means he is fine, but off spring might not be). When we found this out were advised to have a CVS test to determine whether our baby would be genetically ok. The CVS test was carried out by Prof N at Kings and came back fine and I was ecstatic.

Unfortunately when ds2 was born things were not ok - it was found that he only has one kidney and he has global developmental problems. As soon as this became apparent, my sons developmental paediatrician suggested genetic testing. I was absolutely gobsmaked - after all I had had a CVS test - how could it be anything genetic? Anyhow, it now appears that not every single genetic syndrome shows up under standard resolution testing

This was a huge blow to me - as I had really believed that ANYTHING genetic would show up with a CVS test.

Now, my little ds2 might not have a genetic disorder - it is quite possible - and the jury is still out (so to speak), but some of my problems coming to terms with things has been that I had had a CVS test done previously and therefore I had a false sense of security. In fact I was doing cartwheels that this baby was going to be so healthy!

Thomcat - I hope you understand why I am posting this, certainly not to upset you - actually I dont believe it will, because I think you are aware of what I'm saying already... and because testing for Downs and certain other syndromes is absolutely definitive with a CVS test. I just dont want people I did....that absolutely bl**dy everything genetic shows up with a CVS test

heartinthecountry Thu 23-Jun-05 22:31:29

FWIW Merlot I think you are right to post this. My dd's condition is genetic but it cannot be tested for in vitro.

This has always been my issue with testing - not that it exists per se but that it isn't better explained and counselled. But I won't get into that here.

Fio2 Fri 24-Jun-05 07:59:29

Oh merlot iykwim

Merlot Fri 24-Jun-05 08:10:20

Thanks Fio and HITC. HITC the point you have made is the essence of that which I was trying to say - the perception of CVS testing is that it will find out if ANYTHING is wrong genetically.

I know that its not just me that have been shocked by my own experience, but also friends of mine...who can't get their heads round the fact that I had a good result from a CVS test, but that we are now still having to go through genetic testing with ds2

JakB Fri 24-Jun-05 08:11:37

Oh love, I totally respect the fact that you have started this thread. I'm sure TC will understand. She's a very wise woman.

katierocket Fri 24-Jun-05 08:11:56

I imagine this is very rare though merlot

chonky Fri 24-Jun-05 08:13:48

I understand too Merlot....DD's standard and telomere testing has come back as normal, yet I strongly suspect that her condition is genetic - medicine just hasn't advanced enough yet to test for it yet.

clareren Fri 24-Jun-05 08:18:34

Hi Everyone

I just wanted to echo what Merlot has said, because we have just undergone a similar experience. Our 3.5 ds has been diagnosed as having global development delay, and part of the assessment was genetic and chromosome testing on a blood sample from him.

The results found that he has an extra length on one of his chromosome sets and this could be attributable to his delay. Of course no one could have known this, but the reality is that we were not prepared to hear that our son's delay is something none of us had any control over. We just thought he would catch up eventually. We felt wretched for a while, but then decided the best way to deal with it was to accept there was nothing we could have done and to do the best we can for our son to ensure he doesn't miss out on anything.

Sorry to sound so negative, but I do think it is something you are never prepared for and our genetic counsellors were as much use as chocolate teapots, although they were good at doing the concerned head nodding!

tamum Fri 24-Jun-05 08:27:39

I have to say that only a tiny, tiny proportion of genetic conditions will be revealed by CVS testing. It can only ever reveal relatively gross chromosomal abnormalities. If this message is not getting through from health professionals that's a disgrace to be honest. The exception to this is if a specific disease is being looked for- so for example CF can be diagnosed by CVS but will only be tested for if there is a family history- it doesn't just "show up", it has to be looked for.

Merlot, I'm really sorry.

Merlot Fri 24-Jun-05 08:27:58

katie rocket - I am sure you are right...I have no idea about figures....maybe it is a case that the most common genetic abnormalities can be detected.....and obviously there was a real possibility of my ds having a genetic problem o/a my husband having a translocation....BUT and it is a big but....No-one told me that there was any risk that my ds could have something genetic that wouldnt show up on the CVS test!

We had genetic counselling before I actually became pregnant and I was told, when discussing possible abnormalities that if I became pregnant `well you just need to have a CVS test or an AMNIO'. The implication was that it would be definitive....Prof N (top man in the country)carried it out and I was absolutely lulled into a false sense of security.......

The difficult thing to handle for me has been that I have a very healthy, absolutely `normal' ds1 and if I had known that there had been even a shadow of doubt that my second child would inherit something genetic that would not have been detected by a CVS test...I would not have even conceived again .......

Fio2 Fri 24-Jun-05 08:45:04

yes tamum that was my understanding of CVS and amino's too, but of course you know more than moi

Caroline5 Fri 24-Jun-05 09:07:22

Yes - there are plenty of people on here whose children have no diagnosis whose condition is almost certainly genetic - these conditions would never have been spotted in utero unless the testers knew what to look for. It's like looking for a needle in a haystack.

Not sure about the nasal bone part of the test - dd2 seemed to have an enormous nose at her 20 week scan which prompted the scanner to make various remarks about where she got her nose from (looking at me!) Now I realise that her nose wasn't big, it was that her head was so small making her nose look big (Her nose is actually quite small!)

Davros Fri 24-Jun-05 09:40:28

I had CVS with DD and it was made very clear that it would only detect a certain number of conditions and not everything. I still felt it was worth ruling out the things that could be tested for and, like everyone else, had to take my chances with other things. Although autism can't be tested for, I knew there was a high risk without any testing iyswim, so I suppose knowing that without being able to know absolutely still helped us decide what to do.

geekgrrl Fri 24-Jun-05 09:45:22

I was told that not everything shows up on the CVS, and that the result you get the next day is only a preliminary one ruling out major chromosomal abnormalities such as trisomies, the full result isn't available until two weeks later.

I think a lot of people don't seem to realise that most of these tests aren't definite, and that the vast majority of disabilities don't have a genetic cause, anyway. It seems to be a bit of a lottery as to who you see for the testing or screening.

Fio2 Fri 24-Jun-05 11:41:43

Caroline% FWIW my friends daughter has microcephaly and she was scanned ALOT during her pregnancy as her 2nd child was stillborn. they still didnt pick up that she had microcephaly or a genetic syndrome either, even though she also had an amino. Hope you are okay btw

dinosaur Fri 24-Jun-05 11:50:58

I had CVS with DS2 back in 2001. It was made clear to us that all they were doing was counting the chromosomes, nothing more.

yoyo Fri 24-Jun-05 12:18:57

Tamum - CF can only be detected by CVS if the specific mutation of each parent is known. I am a carrier of the most common mutation but DH has a family history. So far he has tested negative for all mutations that can be detected but we still have a statistical risk (we do not intend to have any more children so this will no longer be an issue for us). Basically, they have to know what they are looking for.

Fio2 Fri 24-Jun-05 12:19:56

yes they do have to know which mutation they are looking for thats right

tamum Fri 24-Jun-05 12:36:51

Yes, yoyo, I know.

yoyo Fri 24-Jun-05 12:42:36

Sorry Tamum - just read one of Fio2's earlier posts and realised that you must be well up on this stuff. Are you a geneticist?
When we discovered the CF risk I assumed, like a lot of people, that CVS would give me an answer and was bitterly disappointed to learn that we could have no tests. I think the majority of people have this misconception.

Fio2 Fri 24-Jun-05 12:45:48

they do yoyo!

tamum Fri 24-Jun-05 12:56:21

I am yoyo, yes. It is awful, I know- there are some mutations that are just impossible to find, and even we have our whole genomes sequenced and available on a CD from shortly after birth thre are probably some that will still evade detection. Your case illustrates the point I was trying to make even better, as you just have to know exactly what you are looking for. It's like if you were checking that a toy cupboard had the right number of boxes with everything sorted out properly, you would notice straight away if there was an extra box, or a box missing, but if a piece of lego was missing from the lego box you would never notice unless you know that you had to check the lego box extra carefully.

Sorry if that's taking dumbing down a bit far!

chonky Fri 24-Jun-05 13:09:16

I think that that's an excellent analogy tamum.

yoyo Fri 24-Jun-05 13:10:47

Tamum - I had my three children in three different counties and have had to explain my situation hundreds of times to midwives, health visitors, etc. I wish I had thought of your simple explanation as many of them glazed over when I got onto mutations. Explaining the need to have cord blood taken was even harder.

tamum Fri 24-Jun-05 13:11:17

Thank you chonky . I was trying for ages to think of something and that was the best I could do!

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