Trial of Non Invasive Test for Fetal Genetic Abnormalities
Thursday, February 7, 2008 2:02
Today, most pregnant women in the US undergo a series of tests to determine the risk of their baby having certain genetic abnormalities like Downs Syndrome (trisomy 21) or Edwards Syndrome (trisomy 18). Typically, these screening tests include the maternal serum quad screen, a test of the mother’s blood for levels of 4 different substances: AFP, hCG, estriol and inhibin-A. Some women also undergo first trimester ultrasound screening or other ultrasound procedures. The problem with all of these tests, is that they are only screening tests, which have a relatively high rate of both false positive and false negative results. The only way to verify the results of these screening tests is to look at the chromosomes of the fetus, which must be removed from the uterus by either chorionic villus sampling (CVS) or amniocentesis. Both of these are invasive procedures which carry a risk of miscarriage after the tests are performed.
Now, women may have a new, non-invasive (at least for their baby) way to determine if their baby carries certain chromosome defects. Two companies, Connecticut based Ikonisys and California based Sequenom, are testing systems which will allow them to examine fetal chromosomes circulating in a mother’s blood. Since this method will look directly at fetal genetic material, instead of indirect markers of disease, it should be able to provide a concrete diagnosis as opposed to a risk estimate. If these tests prove to be accurate and effective, they should reduce the stress and unecessary procedures generated by false positive quad screens. In addition, these tests address the needs of women who skip the quad screen altogether because they know they wouldn’t take the risk of having an amnio if their quad screen produced a positive result.
I’ve seen too many women scared and stressed needlessly over abnormal quad screen results, so I hope these new tests prove to be accurate and effective. If the tests are proven to work, would you want to have them during your pregnancy?
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Michelle says:
February 8th, 2008 at 2:32 pm
I would only get this test if what it was testing for would benefit the health of the baby. I didn’t get the quad screen for two reasons, 1) the high rate of false positives, and 2) knowing that my baby had downs syndrome wouldn’t change anything about the pregnancy for me (e.g. I wouldn’t terminate b/c the baby had downs). For me, the stress of these genetic tests isn’t worth it.
Kristie says:
February 8th, 2008 at 5:19 pm
I agree with what you’re saying as far as Downs goes. Edwards/trisomy 18 is fatal though, and many Edwards babies die during or shortly after delivery. I would want to know a diagnosis like that in advance if it was possible. That way we could be prepared, and people who wanted to be on hand to see the baby could make plans to be there in case we didn’t have a lot of time together.
You never know what you’d actually do until you’re placed in the situation, but with my history, I don’t think I’d work so hard to prolong a pregnancy with lots of drugs and bedrest if I knew the baby had a fatal condition. I wouldn’t end it, but I wouldn’t go through hell trying to make it to term either. I would let nature and my body take its own course in that case.
Sue says:
February 8th, 2008 at 5:49 pm
My daughter has a chromosomal condition that was indicated on a first trimester screening ultrasound (followed up by a cvs, which I swore I would never have). But when confronted with the knowledge that our baby had “something”, I found I needed to know what it was. It helped us plan for her delivery – knowing that a cardiologist would be needed – and it gave my husband and I plenty of time to get ahead of the game on educating ourselves. While it made for a stressful pregnancy, it enabled me to be able to enjoy her once she got here.
Kristie says:
February 8th, 2008 at 6:23 pm
Sue – Thanks for sharing your experience. I don’t think I could make it the whole way through a pregnancy if I knew something was definitely wrong and I didn’t know what it was. I’m sure I would have ended up having cvs too if I was in your shoes. We had a minor abnormality (echogenic focus in the heart) on a 20 week scan, and I was pretty much worried sick until the perinatologist did a second scan and told us it wasn’t anything to worry about.
Lisa says:
February 24th, 2008 at 8:31 am
WOW. I am going through It!! On friday I recieved a phone call from my OB. they told me I tested + for low afp which indicated t18/ds. I am 41 and have 7 very healthy children and consider myself healthy also. Initially the nurse called and asked if I could come in asap. I was so scared!!! Then she said let the midwife call you back in 15 min. 2hours (which seemed like a week passed and no phone call.) I was so mad so I called back!1 she’s not here yet.. I was so sick any way immediately I started to research and have been for 3 days finally finding this site! I have so many different thoughts and fears that I just don’t know what to do>>>%&%&? I am in the medical field and know how these people operate and do not particularly trust most of them even with the proper handling of blood work.. I don’t want to be in denial either to the fact that something could be wrong. I am fearful of amnio because I know my bodies sensitive to a lot of things. I was just in the kitchen and said that after the sono I would decide what to do further. What was supposed to be a happy time (pregnancy) has turned into a nightmare and because if this I don’t even feel pregnant any more!!!It’s like I gave up hope! I understand how you feel michelle sometimes not knowing something makes all the difference in the world now I am worried about this test stuff and at the same time so stressed that I feel like I will miscarry and in that case everything would’ve been just a false-positive result. well, life sometimes hands us some really rough things. I just want to see this sono. Thanx for all of your opinions at least I don’t feel alone any more
Kristie says:
February 24th, 2008 at 4:18 pm
Lisa, I’m sorry to hear you’re going through all this stress. It’s very scary. Once you have the ultrasound, I think you’ll have a better feeling about what you want to do next as far as an amnio or more tests. I’ll be hoping that the ultrasound shows a beautifully healthy baby!
Michelle says:
February 25th, 2008 at 7:09 pm
Lisa, I will say a prayer for you and your baby. I have never been through this, but I imagine one of the worst parts is not knowing.
I actually read more about the trisomy 18 and now I am reconsidering. I think it would help to know if your baby had something serious like that so you can prepare. On the other hand, the stress of a possible false positive and all that testing is not something I would want to go through either. It is hard to know what is the right thing.
Sequenom One Step Closer to Noninvasive Test for Down Syndrome | Kristie McNealy, MD says:
February 25th, 2008 at 11:21 pm
[...] I posted earlier this month, there are a couple of US companies working on providing noninvasive prenatal diagnosis for genetic conditions like Down syndrome (Trisomy 21). A recent press release from one of those [...]
Angela says:
March 30th, 2008 at 11:04 pm
Last thursday I also recieved a positve AFP result for tri/18.
My doctor says everything looks great and he doesn’t see anysigns of this in my regular ultrasound. I will be going Friday morning to a specialist. Wish me luck…. And if their are any false positives out there, please let me know.
Angela
Erin says:
March 16th, 2010 at 10:39 pm
Well i too am going thru the stress and worries about the t18. my doctor had told me not to worry until i seen specialist. well i went to him today, and found out exactly what test came back positive. now i know that there werent any abnormalities showing in the ultrasound, but thats never a 100% guarantee. if i knew of a more noninvasive procedure in my area that could guarantee me knowledge of whether or not my baby has t18 i would do it. but instead i am risking miscarriage to have the amnio done asap.
Kristie says:
March 16th, 2010 at 11:07 pm
Erin-
I’m sorry that you’re going through this. Pregnancy can be stressful enough when everything is going perfectly. Good luck with the amnio, and the results!
-Kristie