Genetic Testing Exposes Prenatal Abnormalities

A genetic test has revealed more pertinent information for clinicians than the current routine of prenatal testing.

The test uses microarray analysis to more effectively investigate a fetus' DNA than is currently possible with the karyotyping method, which is a visual examination of the fetus' chromosomes.

A team of scientists led by those at Columbia University Medical Center (New York, NY, USA) conducted a trial of 4,406 patients at 29 centers throughout the USA. The study included women of late maternal age and those whose fetuses were shown to be at an elevated risk for Down syndrome, to have structural abnormalities, or other problems according to an early screening. The study took four years to complete.

In 4,340 of the fetal samples, microarray analysis was successful and 87.9% of samples could be used without tissue culture. Microarray analysis of the 4,282 nonmosaic samples identified all the aneuploidies and unbalanced rearrangements identified on karyotyping, but did not identify balanced translocations and fetal triploidy. Among fetuses in which a structural or growth abnormality had been discovered via ultrasound, microarray detected clinically important chromosomal deletions or duplications in one out of 17 cases (6%) that were not seen using karyotyping. In the women with advanced maternal age or positive screening results, microarray analysis detected an abnormality in one out of every 60 pregnancies (1.7 %) that when tested using karyotyping revealed no abnormality.

Ronald J. Wapner, MD, the senior author said, “Genetic medicine is about obtaining genomic information about an individual and predicting what affect it will have on that person. But we are all different, so genetic abnormality in one person may behave differently than in someone else. For example, an inherited disease could be mild in the mother, but severe in her child. We are studying what these mean clinically, and science continues to catch up with our ability to obtain the information." The study was published on December 6, 2012, in the journal the New England Medical Journal (NEJM).

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