Blood Test for Down Syndrome Could Replace Amniocentesis

Robyn Nazar RN BSN's picture
Baby With Down Syndrome
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The development of a new blood test to detect Down Syndrome may have a significant impact on prenatal testing and decrease the use of the invasive amniocentesis procedure in pregnant women.

Test Predicts With 100 Percent Accuracy

Created by scientists in Cyrprus, this maternal blood test can detect DNA and chemical changes which are present when the mother is carrying a baby with an extra chromosome 21, a condition known as Down Syndrome. The blood test can be done in the 11th week of pregnancy and predict with 100 percent accuracy whether or not the baby will be born with this chromosomal disorder.

According to the researchers, this test is more accurate, less invasive, and less risky than the current method, called an amniocentesis. An amniocentesis requires extracting fluid from uterus through a needle inserted into the abdominal wall. It less than 100 percent accurate in detecting Down Syndrome and increases the mother's risk for miscarriage, infection, and trauma to the fetus. The new blood test completely eliminates all of these concerns.

“Such a noninvasive approach will avoid the risk of miscarriages of normal pregnancies caused by current, more invasive procedures,” said Elisavet A. Papageorgiou, researcher on the study.

Right now this blood test is still being studied and has not been approved for clinical use. However, researchers believe that it will likely enter clinical practice within the next few years. If this happens, it could dramatically change the clinical practice of prenatal care.

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Currently, due to the risks associated with an amniocentesis, approximately only 1 in 10 women undergo the procedure. However, since the blood test completely eliminates these risks we will likely see more women opting for testing and more cases of Down Syndrome detected during the prenatal period. This raises the point that this could lead to an increase in the number of elective pregnancy terminations and decrease the numbers of babies being born with Down Syndrome.

Furthermore, women opting for a blood test may miss out on the chance to detect many other disorders which are tested for in an amniocentesis. The amniotic fluid extracted in the procedure can be evaluated for nearly all chromosomal disorders, hundreds of genetic disorders, and neural tube defects (ie: spina bifida and anecephaly).

Despite these drawbacks, offering couples a less risky and non-invasive way to determine whether or not their child has Down Syndrome will likely appeal to many. In most normal pregnancies the likelihood of a genetic or chromosomal anomaly is slim and the benefits undergoing an invasive procedure such as an amniocentesis may not outweigh the risks.

According to Dr. Rossa W K Chiu, lead author in a similar China-based study on use of blood tests for detecting chromosomal disorders said that though this method “98 percent of the invasive diagnostic procedures could be avoided.”

Reference:
Elisavet A Papageorgiou, et al “Fetal-specific DNA methylation ratio permits noninvasive prenatal diagnosis of trisomy 21.”Nature Medicine (6 March 2011) doi:10.1038/nm.2312 Technical Report

Chiu RWK, et al "Non-invasive prenatal assessment of trisomy 21 by multiplexed maternal plasma DNA sequencing: large scale validity study." BMJ 2011; 342: c7401.

Image Source: Wikipedia Commons

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