A technique called size-fractionation performed on a sample of the mother's blood allows researchers to identify fetal DNA molecules separate from maternal DNA as a way to determine which pregnancies may be at risk for genetic disorders, according to a preliminary communication in the February 16 issue of JAMA, a theme issue on medical applications of biotechnology.
Currently, prenatal diagnosis of hereditary genetic disorders relies on invasive procedures, such as amniocentesis or chorionic villous sampling [prenatal test that detects genetic abnormalities], which are associated with a small, but significant risk of fetal loss, the authors provide as background information.
Ying Li, Ph.D., from University Hospital, Basel, Switzerland, and colleagues analyzed a total of 32 blood samples collected at 10 to 12 weeks gestation between February 15, 2003 and February 25, 2004 in Bari, Italy, from women with risk for Beta-thalassemia (a group of inherited blood disorders that occur with high frequency in the Mediterranean population) in their newborns immediately prior to chorionic villous sampling. Samples in which the father and mother did not carry the same mutation were examined. Four distinct point mutations of the Beta-globin gene were examined. Presence or absence of the paternal mutant allele (gene) was correctly determined in 81 percent to 100 percent of the cases with only one false-positive test.
"Our study indicates that fetal genetic traits involving point mutations can be detected from the analysis of circulatory fetal DNA in maternal plasma …" The authors write in conclusion that their approach is relatively simple, does not need complex machinery and is cost-effective. "This low-cost and use of simple equipment is especially suitable for the screening of at-risk pregnancies in developing countries."