More First Trimester Screening Options

Many women who will deliver a child after the age of 35 opt to have prenatal testing during the first trimester of pregnancy due to the increased risk of genetic abnormalities that come with older eggs.  Until 2012 the most common first trimester screens have been the ultrasound test for fetal nuchal translucency and chorionic villus sampling (CVS). Nuchal translucency screening uses an ultrasound test to examine the area at the back of the fetal neck for increased fluid. CVS is a procedure performed by a maternal and fetal health specialist physician who removes fetal cells for examination using a guided ultrasound.

Non-invasive tests for chromosomal disorders that examine small amounts of DNA from the fetus in the blood of pregnant women and can help diagnose a few genetic disorders starting late in the first trimester started becoming available throughout the U.S. in 2012.

Ob-gyns say the blood tests can pick up about 98 percent of Down syndrome cases with a false positive rate of 0.5 percent – meaning one in 200 babies without Down syndrome will mistakenly get a positive result. For all women who screen positive for Down syndrome or trisomy 13 or 18, American College of Obstetrics and Gynecology recommends referral to a genetic counselor as well as more invasive follow-up testing, such as with CVS or amniocentesis.

The main advantages of the blood tests is they often all but rule out Down syndrome and make more invasive testing unnecessary, according to Dr. Diana Bianchi, head of the Mother Infant Research Institute at Tufts Medical Center in Boston. “The invasive procedures have some very small, but real risks of miscarriage,” said Bianchi, who is also on the clinical advisory board of Verinata Health, which offers a version of the DNA test.

Now genetic testing companies are developing more uses for the blood tests, such as to identify gender and other genetic disorders like Turner syndrome. Running the blood tests now costs $1,200 to $2,700 each, according to Bianchi, but the majority of that is typically covered by insurance.

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