Non-invasive test for fetal RNA offers possible advance over invasive tests
FRIDAY, Sept. 21 (HealthDay News) -- Just a small amount of a mother-to-be's blood could become the lens through which doctors monitor various stages of fetal health and development, a new study suggests.
"It's amazing that all these pregnant women are walking around with the answers in their blood," said Dr. Jill L. Maron, the study's lead author and an assistant professor of pediatrics at Tufts-New England Medical Center, in Boston.
Maron was referring to the fetal genetic material (mRNA) that, according to the study, circulates in a pregnant woman's blood prior to birth. The ability to open this window on fetal status by taking a sample of the mother's blood "can advance the field of prenatal diagnosis," she said.
It could also represent an important advance in the prenatal diagnosis of genetic diseases and genetic monitoring of fetal development because it wouldn't require invasive procedures, such as amniocentesis.
Another advantage of being able to detect fetal mRNA in the mother-to-be's bloodstream is that "it's dynamic," meaning that the biomarkers expected to be found would vary with time and stage of fetal development, Maron added.
DNA is the genetic material that's common to every cell, Maron said. RNA determines what is transcribed from the DNA to make an eye cell different from, say, a hair cell, she said.
"RNA is more real time. RNA changes all the time, according to the stage of development. That dynamic nature is what we're targeting," Maron said.
The researchers said they proved the presence of fetal mRNA in maternal blood in three ways.
Before delivery, the researchers found that the whole blood of nine mothers included fetal genes, such as those for development, sensory perception, and neonatal physiology.
Then the researchers established that these fetal genes found in the mother's blood were unique to the fetus by also identifying them in umbilical-cord blood.
Finally, within 24 to 36 hours after delivery, these fetal genes were no longer found in the mother's blood, providing additional confirmation that they were unique to the fetus, according to the study.
The study was published online Sept. 20 in The Journal of Clinical Investigation.
Dr. Michael Katz, director of research and global programs for the March of Dimes, said the key result of this research may be that it "holds hope for a very safe technique [for prenatal screening] that involves only taking blood from the mother."
Another expert agreed. Dr. Roberto Romero is chief of the perinatology research branch at the National Institute of Child Health and Human Development, part of the U.S. National Institutes of Health, which funded the study.
Romero said the study has "the potential to change the content of prenatal care by adding a new dimension of information. Specifically, the study of fetal mRNA in the maternal circulation can provide information about fetal function, development and response to insults [that] is not available today."
The next step will be to see what fetal mRNA is present in maternal blood in earlier stages of pregnancy, and then to measure the differences in mRNA between an uncomplicated pregnancy and a complicated one.
Romero characterized fetal medicine as the "terra incognita of medicine in the 21st century." He said ultrasound made "the human fetus visible and thus a patient who can be examined, diagnosed, and treated. However, the human fetus remains the most difficult patient in medicine," he added, "because it's relatively inaccessible and it presents diagnostic challenges which are difficult to solve within the womb."
"The study of fetal mRNA in maternal blood can provide information which is neither available or easy to obtain through other means that can help diagnose and likely treat [fetal] conditions that cannot be identified today," Romero said.
For more on genetics and pregnancy, visit the March of Dimes.
SOURCES: Jill L. Maron, M.D., assistant professor of pediatrics, Tufts-New England Medical Center, Boston; Michael Katz, M.D., senior vice president of research and global programs, March of Dimes; Roberto Romero, M.D., chief of perinatology research branch, Intramural Division, National Institute of Child Health and Human Development, National Institutes of Health; Sept. 20, 2007, The Journal of Clinical Investigation, online
All rights reserved