Pregnant women may find out whether their baby is likely to be born with Down syndrome or other genetic disorders by undergoing a prenatal genetic test that appears to be just as accurate but much safer than current methods to diagnose these disorders.

Down syndrome, also called Trisomy 21, is a chromosomal disorder triggered by the presence of all or part of an extra 21st chromosome. This genetic disorder, the most common one, causes mental retardation, unusual facial characteristics, and a high risk of heart defects and occurs in 1 in every 733 infants, according to the National Down Syndrome Society.

Currently, moms-to-be have three options to find out whether their babies have Down syndrome. Either they undergo amniocentesis or chorionic villus sampling (CVS), which require inserting a needle in the uterus, or they skip the tests and miss the chance to learn of genetic defects before birth. Amniocentesis and CVS are done typically after the 15th week of pregnancy and carry a small risk, roughly 1 percent, of causing a miscarriage or birth defects. Despite the small risk, these tests were offered mainly to women 35 or older and others most at risk of having a baby with Down syndrome. Moreover, by the time all these tests confirm Down syndrome, the pregnancy is often 18 or 19 weeks along, making the decision to terminate even more emotionally difficult.

The new test, developed by researchers from Stanford University, California, identifies Down syndrome in a safer way, requiring only a simple sample of the mother’s blood to spot chromosomal disorders such as Down syndrome. The test was used on 18 women at the Prenatal Diagnostic Center at Lucile Packard Children’s Hospital. The women were previously tested for Down syndrome via standard tests. The new test accurately identified the nine women with a Down’s syndrome pregnancy and three others with fetuses with different chromosomal disorders.

“It’s the first universal, noninvasive test for Down syndrome. So this should be the first step in putting and end to invasive testing procedures like amniocentesis and chorionic villus sampling,” said Stephen Quake, a Stanford professor of bioengineering and the study's senior author. He developed the tests after his wife underwent amniocentesis with their first child and CVS with their second. “Both were nerve-wracking experiences,” he added.

The new test could be administered much earlier in a pregnancy than amniocentesis or CVS, potentially as early as five weeks after conception, making the decision to terminate easier from an emotional point of view.

However, more study needs to be done in order to prove the test’s efficiency. In fact, Dr. Quake said the next step is a larger study involving hundreds of women. If effective, the new test could be widely available in two or three years and could become a routine prenatal test of a baby’s health, Dr. Quake added.

The findings of the study were published in the journal Proceedings of the National Academy of Sciences.