Diagnostic tests

[Sid]

I'm 8 weeks pregnant with my third child and am wondering for the first time whether to have any additional tests, other than the 20 week scan, eg. nuchal fold, or blood test for Down's Syndrome. For my first two, I didn't want them as I had no idea what I would do, should I have a high probability of bearing a Down's child. I felt very much on principle that I ought to give birth to the child my husband and I conceived, come what may, as it was our choice and privilege to be able to have children. This time I somehow feel more worried, perhaps because I'm older (35) and also wondering how I will cope with a third (even though I do really want it), let alone potentially a special needs child. What have others done? Have diagnostic tests reassured you? Have you ever had a termination as a result of a test? Have you had a test and ignored the result? I'd love to know.

I had an additional test although we decided that whatever the outcome, we would keep the child. It was just a question of preparing ourselves. As I understand it, the Nuchal fold scan needs to be done at 11 - 12 weeks. I went to the Wolfson Institute in London where they also do a blood test and combine that with the nuchal fold to give you a probability. Obviously it's not fail safe but the only 2 tests that are (amnio and CSV) both carry a risk of miscarriage which at 35, is considerably higher than the statistical risk of a Down's child.

I don't really understand the statistics on Downs anyway. I was told that at 36, I had a 1 in 140 chance of a Downs child. Intuitively, this seems extremely high case given that these days, 36 is not an especially advanced age at which to have a baby.

The nuchal fold test is a good one to have as it is non-invasive and early. Same for the blood tests. I only had these 2 things even though I gave birth at 40 as they showed a low risk (not an absolute!) and I decided against invasive tests on that ground. As we had decided not to terminate for Downs anyway, we did not want to take the risk of miscarriage. If, however, the other tests had shown a high risk would I have had the amnio in order to be sure? It is not easy to decide these things, step by step is usually the best way.

rouble with statistics is that however long the odds are, if you are the 1 at the other end (of 1000-1 or whatever) you are the one who has to cope with the consequences.
when i was pregnant for the 3rd time i was 36 and could have had amnio, but my elder 2 were only 5 and 2 and i was idealistic enough to think i could cope with a downs child.
the 4th time i was 41 and the others were 10,7 and 4 and we were all so busy i knew i couldn't have coped. so i had amnio, with the clear intention of having a termination had the result been bad. fortunately it wasn't. (nobody knew i was pregnant except me and my husband. announcing that i was suddenly 20 weeks preg shook a few people!)
i have a friend with a downs sister - the youngest of 4 children. they are all in their 40s now and from the way the friend talks about her, the other 3 seem to feel that their lives were not improved by her arrival. you have to consider the other children at least as much as the baby...you also have to consider that a downs child would need looking after for decades...when it is 35, you will be 70, and you would still be utterly responsible for it.

Thanks for all your input on this. I'm going on holiday for two weeks next week so probably won't be able to go for the nuchal fold scan (coward's way out), but it'll give me a chance to clear my head (well, as much as going on holiday with two small children will let me clear my head...)and think about the other tests.

I had a nuchal fold scan and afterwards was given a revised risk figure for Downs etc - it has gone fron 1:350 to 1:3500. I found this pretty reassuring and had no other tests ( I was 35 at the time and so was aware of the increased risk.)
I have a friend whose daughter has Downs - this was initially picked up by a nuchal fold scan and confirmed by amniocentesis. Although she never considered terminating the pregnancy, this gave my friend time to plan for her daughter's arrival and it also meant that she had the baby at Guy's with loads of specialists on hand. In the event they weren't needed as the birth was completely normal and the baby didn't require any treatment etc.

I finally got to see my GP last night (had to wait more than 2 weeks for an appointment) in order to ask for a nuchal fold scan. Although I'm 38, he didn't seem to be at all sure as to whether I would be able to have one. As I'm now around 10 weeks, time is running out. I just wondered if anyone knew somewhere in central London where I could get one done privately, preferably without a referral?. Many thanks.

"If the test isn't available in your area and you want one, your GP can refer you to the Harris Birthright Research Centre direct for an immediate test, but since the centre is privately run you will have to pay for it. The current cost is around £100+. Alternatively, you can telephone the centre every day at 10am - 020 7486 0476 - to see if there are any appointment cancellations. Around 90 centres in the UK offer private tests."

I've just lifted this straight from another site. Harris Birthright is at Kings.

I never bothered with tests with my first 2 as I felt I couldn't bear to terminate whatever. However with my third my DH was keen to have the blood test. I think he felt we had been lucky twice and were almost tempting fate. I'm only 31 though. The test gave me a 1:2800 risk so I'm not concerned at all but at the end of the day it is only a risk factor and as someone said there is still the chance you could be the 1.

I had a friend who had a very good nuchal results but then had a baby with downs and had a very tough time. However this was when nuchal scanning first came out so I presume they are more reliable now. However as with the blood test its only a risk factor. 1 in 100 still seems low in every other sense as you have a 99% chance of being OK but most would consider this high risk for downs etc so the stats are confusing. The only way to be sure is to have amnio etc and weigh up the risk of mc. My SIL had high risk blood test and nearly lost the baby after amnio but he was fine. Its a really tough thing to decide. I guess the bottom line is how you would cope with the different outcomes.

I would not terminate in the event of Downs but my real issue is that if I don't get a nuchal, I don't get a scan at all until 20 weeks. I just feel this is too long to wait, particularly if there are any other major problems. In any case, I would like the info that a nuchal scan provides, given my age. Thanks so much for that info Soupdragon - will given them a call.

I had the nuchal fold at 37 and came out quite low risk and felt enormously reassured and decided not to have further tests (the scanner almost insisted that I didn't!). While I was aware that it didn't elimate the risk altogther it really, truly put my mind at rest and made me much happier.

Snap at 39, Aloha. The nuchal scan which I am lucky to get gratis locally also provides an early basic check for anencephaly, spina bifida, presence of heartbeat, limb abnormalities etc, so I can utterly understand why any mother would want an early scan, full stop. Like you, Bells, termination on the basis of high risk for Downs was not an option for me, but I'd much prefer to have a good idea in advance and be prepared.
I am really surprised that you are not offered an early dating scan, Bells, and like SoupDragon, would think that the Harris can help you. Or maybe there are facilities attached to the Lindo Wing at St Mary's? Good luck and let us know how you get on (and how many heartbeats are seen...!)

Have phoned Harris up and all booked, so thanks again. Actually I think my GP is just incompetent. He ummed and aahed for ever and then eventually said that because of my advanced years, I should have an amnio!. I made it clear to him that I had no interest in an amnio under any circumstances but still no offer of a scan. As you say Marina, it's reassurance on all the other bits that I would like as much as the actual nuchal fold.

Just wondering what specifically the nuchal fold scan is testing for - ie is it for Downs alone or does it indicate other chromosomal abnormalities? Just asking as I had the nuchal done with dd2, got a risk factor of approx 1:1900 and now have a child with probable chromosome abnormality (she has unexplained severe learning difficulty and an unusually small head (microcephaly), which doctors feel is probably due to a genetic defect in the egg or sperm, but they can't as yet pinpoint a specific gene as the culprit). Basically, I'm not sure if this sort of thing could be indicated by the nuchal scan. (BTW, don't want to worry anyone, dd is obviously a very rare (and gorgeous !)case).

Just to echo Caroline5's point, no test can detect everything - I had a nuchal scan because of my age (42 when pregnant) & was told I had a 1/250 chance of a down's baby - I then went on to give birth to a DS with a 1/4000 abnormality (fortunately which could be corrected by surgery) so I am 'wary' of tests, don't want to worry anyone uneccessarily, but just be aware that you can't 'test' for everything.

Caroline5 - my DS was born with a craniofacial abnormality, he would have had an unusually large, misshapen head without surgery. Again, as with your daughter, the condition is so rare that no cause has been 'proven' - I don't know if there are any similarities. I got tremendous support from 'Headlines' can give you their details if you haven't come across them yet.

Apolgies if this message appears intrusive, the conditions may be completely different.

bells2 (did you used to be the Bells1 on this thread or is that someone else???) I am really shocked that you had to wait 2 weeks just to see your GP - what kind of Mickey Mouse operation is he running?

Also shocked that your first available diagnostic test is just an ordinary scan at 20 weeks. I thought things were organised much better these days...best of luck with the nuchal thing anyway, hope the results are as good as they can be.

Caroline5: the nuchal fold was developed to specifically look for Down's syndrome. However, what they're measuring (thick skin on the nape of neck) also tends to occur with many other chromosone defects. So, yes, nuchal fold does detect other conditions, but it's best at finding Downs.

From what I read, at best the nuchal fold will only detect 80% of Downs' cases -- that means 20% go undetected. What baffles me is how someone else on Mumsnet got her risk reduced from 1:150 to 1:1735. That suggests the 92% of her risk was removed; the nuchal fold isn't that good, was the hospital assuming that nuchal fold really has a 100% detection rate????...

Blame me for thinking I understand probability, but i can't work out the numbers any other way. A 90% reduction in risk would reduce one's odds to 1:1500... how do they come up with 1:1735??? I fear that somehow the risk numbers are generated wrong, sometimes.

Lindy, thanks for the offer of info, your message wasn't at all intrusive, unfortunately I don't think dd's condition is connected to your ds's - was it craniosynostosis? They checked for this, but her skull is formed normally. Her brain hasn't grown at a normal rate, so her head remains smaller than it should be.

Bells2, glad you have got your scan arranged and hope that you'll be fully reassured. I agree with janh that your GP needs to get his act together!

Zebra, thanks, our posts crossed. Yes, these risk factors do sound overly exact, if they are not 100% accurate in the first place. With dd1, I got a risk of something like 1:9000, which seemed fairly conclusive (she is fine!) Perhaps I should have compared the two results of our dds (only two years apart, and I was still under age 35) and thought 1:1900 a large increase in risk for the second one??? Anyway, it's all water under the bridge for us now....

Caroline5 - yes, his condition was craniosynostosis, we were 'lucky' as it can be corrected surgically if detected early enough.

Zebra, the 2 risk factors are based on comepletely different 'tests'. One is purely based on the age of the mother related, the other based on a scientific measurement of that particular baby. I guess it's like comparing your risk of a car accident statistics based on the colour of your car and then based on your age/experience.

To a mother of X age, 1 baby in every 150 would be affected by Downs - this risk is based on looking at the mother only. By looking at the specific baby she is carrying, 1 in 1735 babies with that nuchal fold measurement would be affected by Downs. (I can't remember if they take into account the mother's age risk into the final figure or not)

When you have your nuchal scan, you send in a "result sheet" to let them know if your baby is healthy when it is born. I imagine they use this information to update their statistical model.

Does this help?

I meant "One is purely based on the age of the mother" Ignore the rather odd 'related' that has crept in!

Thanks Soupdragon -- that makes sense (in terms of how the stats are given out). I don't see how they can possibly take into account mother's age when doing nuchal fold and get better stat than 1:750 for a mother age 36. Based on the fact that Nuchal fold can only detect 80% (at best), I still couldn't see how my individual risk at age 36 could be reduced beyond a certain factor; they can only tell me that 80% of my risk was removed. Or 1/5 * 1/150 = 1/750.

I am, as you might guess, more concerned about false negatives than false positives.

My memory of this is a bit fuzzy, because it was a couple of years ago, but i spent a day watching Nuchal Fold scans being done at the local maternity unit. As I recall the mothers age and the babies measurement are entered on a computer, and the computer kindof cross references them on a chart and pops out a "risk factor" for that particular baby having Downs. I have seen older women with really low risk factors, and younger women with much higher ones than you would expect, so it IS possible Zebra for your risk factor to be decreased hugely. But do remember that it IS only a risk factor - not a diagnosis. As has been commented, you could get a 1:1000 risk, and be that one person - conversley you could get a 1:2 risk and it be fine.

Remember that the basic risk factor which applies before the scan is an average risk of all women of a certain age to have a Downs baby. After the scan the number you are given is based upon women of that age with a bay with those measurements - which in theory is a lot more sensitive and can alter the statistics dramatically.

Personally I don't like the nuchal Fold test - I believe that it worries people unnecessarily, and since it doesn't give a determinate answer I can't really see any real value in it. But that is just my opinion, of course!