Two new techniques, one using maternal blood and the other amniotic fluid, should give health care providers new insight into the health of a baby before birth.
Unlike currently available prenatal genetic tests, such as amniocentesis, the test using maternal blood is less invasive and can detect genetic disorders, such as cystic fibrosis and thalassemia, a group of inherited blood diseases that includes anemia. The second test examines the amniotic fluid collected during amnio centesis, but provides far more information on gene expression and fetal development compared with currently available tests.
Less Invasive Procedures
Although both tests are currently in the preliminary stages of development and are not yet commercially available, experts are optimistic about their potential.
"The genetic analysis of the fetus currently relies on invasive procedures, such as amniocentesis, which is associated with a risk to mother and unborn child," says Sinuhe Hahn, co-author of the study that focused on the maternal blood test, and director of the Laboratory for Prenatal Medicine at University Women's Hospital in Basel, Switzerland.
The experimental blood test can analyze fetal DNA in the mother's blood. This can be done because researchers recently discovered how to separate fetal DNA from maternal DNA, says Hahn.
Pinpointing Mutations
In their experiments, the researchers drew blood samples from 32 pregnant Italian women at risk for a genetic mutation for thalassemia, a type of anemia that is common in people of Mediterranean descent.
Using its newly developed technique, the Swiss team correctly identified an inherited defective gene in fetal DNA for between 81% and 100% of the cases.
Hahn says the biggest advantages of this test are that it is both less invasive and relatively cheap. The technique may also be useful for spotting serious conditions and illnesses such as cystic fibrosis and Tay-Sachs disease in the fetus, she says.
More Genetic Study From Amniocentesis
The other technique involves a new use for amniotic fluid that is usually discarded after amniocentesis.
In a typical amniocentesis, cells are collected from the amniotic fluid and fetal chromosomes are then studied to look for problems such as Down syndrome. Once those cells are removed from the sampled amniotic fluid, the remaining fluid is generally discarded.
But a study reveals that valuable information is still locked inside that fluid, says Dr. Diana Bianchi, vice chair of pediatric research at the Floating Hospital for Children and Tufts-New England Medical Center, Boston.
What we found is that in the amniotic fluid itself, (there] is vital information about the fetus," says Bianchi, co-author of the study. By examining the fluid, her team was able to obtain information on thousands of genes and their patterns of expression.
Developmental Clues Revealed
For their study, the researchers focused on only those genes they thought would be developmentally important. For example, salivary mucin is an important substance for the oral digestion of food, says Bianchi. In the amniotic fluid of one 17-week-old fetus the investigators found no evidence of salivary mucin, which Bianchi says wasn't surprising because the developing fetus has no need of orally digesting food.
However, in fluid samples from near-term fetuses, the researchers did find salivary mucin, suggesting that as a baby nears birth a gene that tells the body to make salivary mucin gets switched on.
A more significant finding was in a set of twin fetuses. The gene that directs the body to make certain proteins involved in lung development was turned on in one baby, but not in the other. The baby without these proteins did not survive.
Bianchi says one of the most important uses for this test might be for women in preterm labor. It could give health-care providers a much more accurate way to assess the fetus's developmental progress than is currently available.
"If you're going to do an amniocentesis anyway, for the same risk, you can get much more info," says Bianchi.
