# Mother's blood holds genetic clues to fetal health



## Redcap (Oct 26, 2006)

This is an article from New Scientist online.

I can't geive you a link as it is subscription only.

Mother's blood holds genetic clues to fetal health

Tiny genetic fragments from the fetus circulate in pregnant women's blood before they give birth, a new study reveals. The finding means that doctors might one day be able to test for a wide range of congenital diseases without the need for invasive procedures. It could also shed light on fetal development during pregnancy.

Doctors sometimes use an invasive procedure called amniocentesis to gauge fetal health. It involves inserting a needle into the uterus to obtain a sample of fetal DNA.

Amniocentesis carries a risk of injury to the fetus and a less than 1% chance of miscarriage. Other non-invasive ways of examining a fetus, such as ultrasounds, do not provide a full picture of the baby's development.

In recent years researchers have devised a number of non-invasive ways to analyse maternal blood for signs of disorders such as Down's syndrome. These tests work by picking up DNA and other genetic fragments such as messenger RNA (mRNA) from the placenta - an organ that develops out of the embryo and therefore contains the same genes as the baby itself. During the first five weeks of pregnancy the placenta sheds cells into the mother's bloodstream.

However, genetic fragments from the placenta cannot provide a full picture of fetal development. This is because the pattern of gene activity varies from one organ to another. In other words, the genes that become activated in the baby's eye, for example, might not get switched on in the placenta.
Gene evidence

Jill Maron of the Tufts-New England Medical Center in Boston, Massachusetts, US, and her colleagues now have evidence that messenger RNA from the fetus itself - not just the placenta - leaks into pregnant women's blood.

"This is a critical step. It could help us better understand how the fetus is developing," says Dev Maulik at the Truman Medical Center in Kansas City, Missouri, US, who was not involved in the research.

Maron sampled blood from nine pregnant women before they underwent scheduled Caesarean sections. Immediately following the delivery, she and her colleagues took fetal blood from the umbilical cord. A day later the team returned and took blood samples from the same women, all of whom had delivered healthy babies.

Using special microarray technology, the team determined the presence of 20,000 genes based on the messenger RNA in the three sets of blood samples. The analysis identified mRNA for 157 genes circulating in the women's blood before, but not after, delivery. The mRNA fragments of these same 157 genes were also highly prevalent in the fetal blood samples.

Moreover, many of the 157 genes are linked to very specific aspects of fetal development such as the growth of the nervous system, and the development of a sense of smell. Maron says one would not find signs of such genes from the placental mRNA, so the genetic fragments must have leaked through the placenta from the fetus itself.
Regular checks

Maron suggests that fragments of fetal mRNA appear in maternal blood beginning in the second trimester, once the baby starts to produce its own blood.

She says research is now needed to see if would be possible to regularly examine a pregnant woman's blood for changes in fetal mRNA that signal irregular development of the embryo. For example, abnormal changes in heart and nervous system genes might signal a congenital heart defect or spina bifida, respectively.

"What this does is it broadens what we know is possible," she says, adding that understanding the changes in fetal gene activity might one day lead to ways of treating certain illnesses before birth.

Roger Newman, former president of the Society for Maternal-Fetal Medicine and a professor of obstetrics at the University of South Carolina in Charleston, US, agrees the new findings may pave the way towards new non-invasive prenatal tests. But he cautions that they are " still a long way off".

Journal reference: Journal of Clinical Investigation (DOI: 10.1172/JCI29959)


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