New prenatal genetic test 'much more powerful at detecting foetal abnormalities'

Testing a developing foetus' DNA through chromosomal microarray (CMA) provides more information about potential disorders than the standard method of prenatal testing, which is to visually examine the chromosomes (karyotyping), according to a new study.

The results of the 4,000-plus-participant clinical study are being presented at the 32nd annual meeting of the Society for Maternal-Foetal Medicine in Dallas.

In women having routine prenatal diagnosis, CMA detected additional genetic abnormalities in about 1 out of every 70 foetal samples that had a normal karyotype. When a birth defect was imaged by ultrasound, CMA found additional important genetic information in 6 percent of cases.

These results suggest that CMA may soon replace karyotyping for prenatal testing, says Dr Ronald Wapner, director of Reproductive Genetics at NewYork-Presbyterian Hospital/Columbia University Medical Center and vice chairman for research and professor of obstetrics and gynaecology at Columbia University College of Physicians and Surgeons.

"Why would anyone want to continue to use the standard method, which gives only part of the answer?" says Dr Wapner, who led the 34-center study funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

"However, we will have to carefully transition this information into clinical practice - to educate physicians and patients, develop guidelines for its use, and learn how to best use it to improve care," he added.

CMA is not routinely used for prenatal testing but has become the primary genetic test to evaluate newborns with birth defects, as well as infants and young children with developmental delays.

"With karyotyping, we can see only when pieces of the genome of about 5 million base pairs are missing from a chromosome. With CMA, we can see missing pieces of fewer than 100,000 base pairs," Dr Wapner said.

CMA is based on a method that determines whether the right amount of genetic material is present at numerous locations in the foetus' genome.

The study was recently published in the American Journal of Obstetrics and Gynecology. (ANI)