Researchers find new technique to identify fetal genetic material from amniotic fluid

A preliminary report suggests that cell-free fetal messenger RNA (ribonucleic acid) can be extracted from amniotic fluid (fluid around the fetus), and then be analyzed to study gene expression changes that may reflect the well-being of the fetus, according to a paper in the February 16 issue of JAMA, a theme issue on medical applications of biotechnology.

In background information in the article, the authors write that fetal monitoring in the womb is now "limited to noninvasive methods such as measurement of uterine size or anatomic evaluation by fetal sonography. In addition, genetic analysis can be performed on amniotic fluid components …" They add that the "cell-free component of the amniotic fluid is discarded after these analyses and is therefore available for research and future clinical applications."

Paige B. Larrabee, M.D., from Tufts-New England Medical Center, Boston, and colleagues analyzed four samples of cell-free amniotic fluid from pregnant women between 20 and 32 weeks' gestation and who had certain conditions that required procedures to reduce an excessive amount of amniotic fluid. The control group in this study was 6 pooled amniotic fluid samples from women at 17 weeks' gestation who were undergoing amniocentesis (removal of amniotic fluid to test for hereditary diseases and congenital defects in the fetus). "After extraction from the normally discarded fraction of amniotic fluid, RNA was amplified twice, labeled, and analyzed using gene expression microarrays." The researchers were able to study the expression of developmental transcripts, such as for certain proteins.

"Preliminary analysis suggests that gene expression changes can be detected in fetuses of different sexes, gestational age, and disease status," the authors report. "Cell-free mRNA in amniotic fluid appears to originate from the fetus and not the placenta." In conclusion the authors write: "The intriguing gene expression differences observed suggest that this technology could facilitate the advancement of human developmental research, as well as the cultivation of new biomarkers for assessment of the living fetus."

(JAMA. 2005; 293:836-842. Available post-embargo at JAMA.com)

Editor's Note: This study was supported by a grant from the National Institutes of Health. Co-authors Drs. Larrabee, Johnson, and Bianchi have filed for patents for the methodology described in this article.

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