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New prenatal genetic test gives parents more answers
A new genetic test can identify potential developmental delays in a fetus or determine why a pregnancy failed, researchers say.
December 6th, 2012
04:41 PM ET

New prenatal genetic test gives parents more answers

New applications of a genetic test could help parents learn more about the genetics of their unborn children.

Three studies released Wednesday in the New England Journal of Medicine highlight the use of microarray testing as the latest technology in chromosome analysis.  Researchers suggest using this test to identify potential intellectual disabilities, developmental delays, autism and congenital abnormalities as well as determining why a pregnancy failed.

During pregnancy a number of tests are suggested by the American College of Obstetricians and Gynecologists based on the mother's age, medical history or ethnic or family background, along with results of other tests. Chromosomal microarray analysis is a genetic test that finds small amounts of genetic material that traditional testing such as karyotyping cannot detect.

The genetic material is obtained during a regular amniocentesis (where small amounts of amniotic fluid and cells are taken from the sac surrounding the fetus and tested during the second trimester of pregnancy) or another commonly used test called CVS, or chorionic villus sampling (where a small amount of cells is taken from the placenta during the first trimester). 

According to one study, this prenatal testing surpassed standard testing to detect more genetic abnormalities. Lead study author Dr. Ronald Wapner, says with microarray, doctors don't look at chromosomes and are able to evaluate smaller pieces of DNA.

If potential development issues are found, "we are way better able to counsel parents about what they would mean for the child," Wapner says. "... We can modify the course and improve the outcome for the child." This type of testing can also be helpful to researchers, as learning what genes cause certain problems may lead to development of potential cures and treatments, he says.

Adequate counseling for parents is needed in case tough decisions need to be made regarding the pregnancy, given the testing outcome, Wapner says.

Dr. Nancy Rose, chair of the American College of Obstetricians and Gynecologists' committee on genetics, says the organization is going to review the studies but can't comment on them yet. However, Rose, who is also the director of reproductive genetics for Intermountain Healthcare, says as a reproductive geneticist, "It's a great promising new technology, but the clinical application really needs some careful evaluation" because of any potential ethical issues.

The second study examined microarray testing in relation to stillborn babies. According to the National Institutes of Health, 1 of every 160 births in the United States is a stillbirth. Parents and doctors often don't know why the babies didn't survive. In this study researchers were able to help parents better understand the reason their baby didn't survive and provide them with information that may one day lead to a successful pregnancy. The microarray testing can be done on tissue that is not alive, where previous tests require live tissue.

"It's a great test for patients who have a pregnancy loss," says Rose, "... and it's superior to detect genetic changes in fetuses that have birth defects."

The third paper was a case report of a specific genetic condition that was not detected prenatally by karyotyping, ultrasounds or the microarray testing, underscoring the limitations to these tests and the potential advantage of the genetic sequencing approach.


soundoff (10 Responses)
  1. jonathan dann

    be careful with a CVS... our 1st born child had a very rare genetic abnormality (deletion of short arm of chromosome 1)that happened at point of conception. both parents were later tested it did not come from either of us. This rare deletion has cause severe delays across the border, physical, mental etc..we have a special needs kid (this is a very difficult life for all)
    we wanted to have another child and were advised to do a CVS (cronic vila sampling)..we did this..the dr did not get enough tissue and had to do the procedure again 5 days later. we were very apprehensive about this , but did it anyway. Then a few weeks later the dr called to say all chromosomes were perfect and we had a healthy baby boy on the way, we were thrilled. then the worst happened my wife started to leak amnionic fluid. The dr had punctured here and all the fluid eventually leaked out and the baby died at 5 months...a horrible experience...the dr downplayed the risk when we signed up for the test, but we wanted to do it bc we did not want to have another special needs child. in speaking with my sister in law , a doctor herself told us that she nows know of only 3 people who have done the CVS..and ALL have lost the baby in the 2nd trimester..by slow leak...this was very dramatic for us..and we considered a lawsuit..so parents please be careful...if you really want to know amni is the way to go..far less intrusive

    December 6, 2012 at 19:38 | Report abuse | Reply
    • Jay

      Sorry for your loss. However I must say that cvs is a safe procedure but it should only be performed by a high risk ob at a specialty center. The increased risk of pregnagncy loss when you compare amino to cvs is thought to be higher because many of the pregnancies lost after cvs would have been lost anyway with the 60% miscarriage rate in the first trimester . The actual loss rate from cvs is less than 1% when performed by a specialist

      December 6, 2012 at 20:07 | Report abuse |
    • msp

      I'm trully sorry for your loss and horible expereinece with CVS, but it does not always end that way. We have 2 healthy kids, 5 years apart. I had to have amnio done with my eldest and that was not a bad experience-didn't hurt at all, gave us a clear answer and piece of mind for the rest of the pregnancy. Unfortunatelly, in the next few years I had two miscarriages, so the last time I got pregnanat I was ready to do whatever I had to do to find out if everything was OK with the baby. And I wanted the answer as soon as possible because I didn't want to let myself hope that this time I might have a baby only to loose it again. Well, I had a CVS and the procedure itself was very painful and uncomfortable. I spent the next few days resting and that was it. Now I have a beautiful baby girl and I'm happy that I had done the CVS. I could relax after the procedure and enyjoy the rest of my pregnancy. My point is: CVS is more dangerous than amnio, but it will give you the answer you need at leat 4 weeks sooner than amnio. And that can make a lot of difference for some people.

      December 6, 2012 at 20:13 | Report abuse |
    • anne

      Sorry for your loss. When I was pregnant, because of my age, I was told by my doctor about these tests options, and had to be performed by a different doctor, a specialist, but also told me there is a risk to lose the baby after performing these tests, so we didn't do it. At same time a friend of my husband that was also pregnant had these test done, and then after she lost the baby, a healthy baby. Most of the times you don't lose the baby but there is a risk. In my case, special needs or not I wanted to have the baby anyway, and my high risk number factor was because of my age only.

      December 6, 2012 at 21:59 | Report abuse |
    • john

      jonathan, the deletion you spoke of...is it Cri Du Chat?

      December 6, 2012 at 22:15 | Report abuse |
    • bluerose

      I'm very sorry for your loss. I too lost a child in the 2nd trimester (25 weeks) for a different reason and that was unexpected and traumatic. Technology these days is amazing. There is now a blood *diagnostic* test (so ZERO risk to the fetus) in discovering Trisomy 21 and can be done very early too starting at 10 weeks. Granted there are other trisomies but this is the most common .. and is what I did for my last pregnancy as I wanted to avoid CVS and Amnio if possible to give us peace of mind. It is an out of pocket expense but worth it. Search for the company Sequenom. It is over 98% accurate. My baby is happy and healthy 7 months old.

      December 11, 2012 at 14:56 | Report abuse |
  2. David Jones

    While a regular chromosome study and many genetic tests can be done by amniocentesis or a CVS, where the trade-off is earlier information with the CVS versus safer test with the amniocentesis, there are some genetic tests that require far more DNA than an amniocentesis can produce—those tests require a CVS—and that could be the reason someone is doing a CVS in the 2nd trimester when we would usually recommend an amniocentesis since it is safer.

    December 6, 2012 at 21:36 | Report abuse | Reply
    • jay

      you obviously do not have any actual knowledge on the subject. both tests require culture of the sample to get enough DNA so it does not matter which one you do, except that the CVS is performed in the 1st trimester not second as you suggest

      December 6, 2012 at 22:01 | Report abuse |
  3. ann

    I had the CVS at 11.5 weeks and it was painless (just momentarily uncomfortable). The only difficult part of the procedure was waiting the 10 days for the results. I decided to go with the CVS because I did not want to wait until 20 weeks for amnio. I was grateful to have the peace of mind, knowing that my baby was healthy, early on in my pregnancy. Another added benefit was learning the sex of the child (optional) along with my test results.

    December 6, 2012 at 23:31 | Report abuse | Reply
  4. JStolz

    Both tests have come a long way in regards to safety. However, unless you are generally worried, I would say neither test is needed. Genetic lottery has already drawn its winner.

    December 9, 2012 at 02:03 | Report abuse | Reply

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