A new study found that scanning the genes of children before they are born reveals significantly more potential health risks than current prenatal testing.
Researchers found that the new test, called chromosomal microarray, detected more genetic abnormalities that could result in genetic disease, like missing or repeated sections of genetic code, compared to karyotying, the standard method of prenatal testing.
For instance, babies missing a portion of chromosome 22 will be born with DiGeorge syndrome, a condition that can lead to severe heart defects and developmental delays. Researchers found that while this missing section of the chromosome was detected by a chromosomal microarray, the missing section was not was not found by the karyotype test. Chomosomal microarray tests also found some genetic changes linked to autism that wasn't revealed by karyotyping tests.
The study published Dec. 5 in the New England Journal of Medicine suggests that microarray should replace karyotyping as the standard method of finding genetic irregularities in women with high-risk pregnancies.
Ronald Wapner, vice chairman of research at Columbia University Medical Center's department of obstetrics and gynecology in New York, said that the test might also eventually be offered to all pregnant women, according to Businessweek News.
Microarray tests are already used to diagnose problems in newborns with developmental delays, autism and congenital anomalies, Lorraine Dugoff, a physician and associate professor of obstetrics and gynecology at the University of Pennsylvania, wrote in an editorial accompanying the studies, the question is when these tests should be given because doctors don't know the meaning of everything they find.
"These reports highlight the power and complexity, and some of the pitfalls, of using new genomic technology in clinical practice," Dugoff wrote. "Chromosomal microarrays can detect almost all the chromosomal imbalances" found with older tests, in addition to much smaller changes, she said.
Experts warned that microarrays could sometimes provide more information than is useful. They explained that because some of the variants found in the genetic tests are new and have unknown or uncertain consequences, the tests could case stress and anxiety for parents who may be considering terminating the pregnancy.
Microarray tests are also two or three times the $500 to $600 price of conventional tests.
The conventional karyotype tests are performed using samples taken from the amniotic fluid or placenta. The sample cells are examined under a microscope allowing researchers to see whether there are too many or too few chromosomes or if they have an abnormal structure.
In contrast, microarray tests, which are much more precise, compare a sample of the fetus' DNA with that of a healthy person. The tests can also look at specific locations to spot much smaller changes, as well as chromosome pieces that are missing or overrepresented.
"The biggest advantage of microarray is it can give us a lot more information," Wapner said, according to Businessweek. "We are expanding the information a person can get out of prenatal testing, identifying additional and more serious problems.