New applications of a genetic test could help parents learn more about the genetics of their unborn children.
Three
studies released Wednesday in the New England Journal of Medicine
highlight the use of microarray testing as the latest technology in
chromosome analysis. Researchers suggest using this test to identify
potential intellectual disabilities, developmental delays, autism and
congenital abnormalities as well as determining why a pregnancy failed.
During
pregnancy a number of tests are suggested by the American College of
Obstetricians and Gynecologists based on the mother's age, medical
history or ethnic or family background, along with results of other
tests. Chromosomal microarray analysis is a genetic test that finds
small amounts of genetic material that traditional testing such as
karyotyping cannot detect.
The genetic material is obtained during
a regular amniocentesis (where small amounts of amniotic fluid and
cells are taken from the sac surrounding the fetus and tested during the
second trimester of pregnancy) or another commonly used test called
CVS, or chorionic villus sampling (where a small amount of cells is
taken from the placenta during the first trimester).
According to
one study, this prenatal testing surpassed standard testing to detect
more genetic abnormalities. Lead study author Dr. Ronald Wapner, says
with microarray, doctors don't look at chromosomes and are able to
evaluate smaller pieces of DNA.
If potential development issues
are found, "we are way better able to counsel parents about what they
would mean for the child," Wapner says. "... We can modify the course
and improve the outcome for the child." This type of testing can also be
helpful to researchers, as learning what genes cause certain problems
may lead to development of potential cures and treatments, he says.
Adequate
counseling for parents is needed in case tough decisions need to be
made regarding the pregnancy, given the testing outcome, Wapner says.
Dr.
Nancy Rose, chair of the American College of Obstetricians and
Gynecologists' committee on genetics, says the organization is going to
review the studies but can't comment on them yet. However, Rose, who is
also the director of reproductive genetics for Intermountain Healthcare,
says as a reproductive geneticist, "It's a great promising new
technology, but the clinical application really needs some careful
evaluation" because of any potential ethical issues.
The second
study examined microarray testing in relation to stillborn babies.
According to the National Institutes of Health, 1 of every 160 births in
the United States is a stillbirth. Parents and doctors often don't know
why the babies didn't survive. In this study researchers were able to
help parents better understand the reason their baby didn't survive and
provide them with information that may one day lead to a successful
pregnancy. The microarray testing can be done on tissue that is not
alive, where previous tests require live tissue.
"It's a great
test for patients who have a pregnancy loss," says Rose, "... and it's
superior to detect genetic changes in fetuses that have birth defects."
The
third paper was a case report of a specific genetic condition that was
not detected prenatally by karyotyping, ultrasounds or the microarray
testing, underscoring the limitations to these tests and the potential
advantage of the genetic sequencing approach.
