Baby Genome Mapped in Womb
A new noninvasive procedure may one day allow women to test their unborn babies for more than 3,500 genetic disorders. It could perhaps replace amniocentesis in which a probe is inserted through a woman's abdomen, extracting a small amount of amniotic fluid to test for abnormalities in the fetus.
Scientists at the University of Washington took blood samples of a woman who was 18 weeks pregnant, and saliva from her partner to map the fetus's DNA. The method was then repeated in another couple.
They then reconstructed the genetic code of the unborn baby, then tested the accuracy of the results by using umbilical cord blood after the baby was born.
"The primary significance of this is that … it may broaden the availability of genetic screening to more patients, while at the same time screening for much larger panels of disorders than can currently be detected," said Jacob Kitzman, lead author of the study.
The new procedure can test for, among thousands of diseases, spina bifida and Down syndrome, the most common genetic disorders in the U.S. , and is safer than amniocentesis.
"This is an incredible breakthrough with huge ethical implications," said Art Caplan, a professor of medical ethics at University of Pennsylvania Medical Center.
Caplan said today's amniocentesis testing was relatively "crude," and new advances would allow more people to obtain reliable genetic information about their children.
Miscarriage is the primary risk of amniocentesis - the uterus can become infected, the water can break or there's premature labor. The risk of miscarriage ranges from one in 400 to one in 200.
About 200,000 amniocentesis procedures are performed every year in the U.S., according to Mayo Clinic, but "with accurate testing that poses no risk, this new form of genetic testing is likely to be offered to every women and family who is pregnant if the cost is low," said Caplan.
While researchers said they don't believe these findings will have an impact on genetic test in a clinical setting in the immediate future, they hope follow-up work will bring technical and methodological improvements that will allow for an easier-to-apply, more accurate and less costly version of the test.
When the time comes for the procedure to be used in a clinical setting though, Kitzman said clinicians would face the challenge of interpreting these results and communicating them with expectant parents - both the results themselves and the uncertainties that come with them."
While these advances will help better understand risk factors for illness, Caplan predicted "they will be among the most controversial forms of testing ever to appear in medicine as the debate over abortion and disabilities both shift to whole genome genetic testing."
While the ethical questions that have always surrounded prenatal testing will not disappear with the new procedure, Kitzman said the "noninvasive tests may provide some advantage by posing less potential risk to the fetus."
"In my experience, full information for parents permits ethical decisions for a family," said Dr. F. Sessions Cole, professor of pediatrics at Washington University School of Medicine at St. Louis. "A longer term ethical issue concerning the ability to predict disease development in later childhood or adulthood from fetal DNA will also need to be addressed. Hopefully, this new information will prompt development of nutritional, pharmacologic, behavioral, environmental, and other strategies to reduce genetic disease risk."