Simple Blood Test May Detect Down’s Syndrome During Pregnancy

Using existing technology, researchers are hopeful that a simple blood test that can detect fetal DNA in expectant mothers will be able to diagnose Down’s syndrome as early as 8 weeks after conception. Unlike invasive procedures such as amniocentesis and chorionic villus sampling (CVS), the test poses no risk to the fetus.

Down syndrome occurs when a child has three, rather than two, copies of the 21st chromosome. The condition causes mild to moderate impairment of cognitive ability. Common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. Down syndrome increases the risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer's disease, childhood leukemia, and thyroid conditions. One in every 733 babies is born with the condition.

The blood test uses an existing test, multiplex ligation-dependent probe amplification (MLPA), to identify DNA from the fetal Y chromosome in maternal blood and researchers are now working to evaluate the technology’s ability to detect trisomy 21 (Down syndrome), as well as trisomy 13 (Patau syndrome) and trisomy 18 (Edward syndrome). The test requires only a small blood sample from the mother, making it much safer than sticking a needle in the uterus as required by the amniocentesis, or using of CVS, which requires snipping off a small piece of the placenta for analysis. Both invasive procedures carry a risk of causing a miscarriage or birth defects.

“Although we need to test and refine this MLPA technique further, our results so far are promising,” said clinical geneticist Suzanna Frints, Ph.D. of Maastricht University Medical Centre. “This is innovative translational research, and when we succeed in developing the MLPA procedure for use in maternal blood, we will be able to offer a safe, cheap, fast, reliable, and accurate noninvasive test, which will be of immediate benefit to pregnant women.”

Although Down syndrome is the most commonly occurring chromosomal condition, this test will also have the ability to identify both Edward and Patau syndromes. Edward syndrome is a condition that is caused by the presence of three, as opposed to two, copies of chromosome 18 in a fetus or infant's cells. The syndrome occurs in about one in 3,000 pregnancies and approximately one in 6,000 live births and has a very low rate of survival due to heart abnormalities, kidney malformations, and other internal organ disorders. Patau syndrome occurs with an additional chromosome 13. The condition causes numerous physical and mental abnormalities, with the most predominant being heart defects, and kills more than 80 percent of children in infancy. Patau syndrome affects approximately 1 in 12,000 live births.

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