Should Standard Prenatal Screening be Scrapped?

Researchers suggest that a new prenatal DNA test should become the new standard to detect Down syndrome in fetuses.

Feb 28, 2014
Bob Grant

WIKIMEDIA, INFERISA new technology is capable of detecting Down syndrome in unborn babies better than the current standards of ultrasound tests and biochemical blood tests, according to recently published research. The study, which appears in the latest edition of the New England Journal of Medicine (NEJM), found that massively parallel sequencing of maternal plasma cell-free DNA (cfDNA testing) resulted in fewer false positives and higher positive predictive values for trisomies 21 and 18 than did standard prenatal screening conducted in even low-risk pregnancies. At present, cfDNA testing is more commonly used in high-risk pregnancies; the new technology is not typically used in all pregnancies.

The study “augurs well for pregnant women and their fetuses: a negative result on cfDNA screening obviates the need for invasive testing and thus the discomfort and risk to the pregnancy incurred by such testing,” wrote NEJM deputy editor Elizabeth Phimister and Michael Greene of the Massachusetts General Hospital in an editorial accompanying the paper. Positive results from standard screening methods, such as ultrasound and testing the mother’s blood for proteins associated with fetal deformities, accurately point to Down syndrome in only about 4 percent of cases. And if one of those screens indicates a problem, invasive methods, such as amniocentesis, must be performed to substantiate the results. The study’s authors found that cfDNA testing more than 1,900 pregnant women, however, correctly flagged trisomy 21 more than 40 percent of the time.

“If [cfDNA testing] were to be used as a primary screen, it could result in a 90 percent reduction of invasive procedures,” Richard Rava, chief scientific officer of Verinata, the division of biotech company Illumina, which sells the test, told MIT Technology Review. Verinata is but one of several firms offering non-invasive prenatal genetic tests.