Pregnant women can have prenatal testing performed during their pregnancies to determine whether or not their baby could have certain disorders. Two types of tests are chorionic villus sampling (CVS) and amniocentesis, which both involve inserting needles into the abdomen. Both procedures are also associated with a small increase, about one percent, of the chance of miscarriage. Scientists have now developed a new noninvasive method in which the blood of pregnant people can be used to screen for genetic variants that may be present in the fetus. The work has been reported in the New England Journal of Medicine.
In this study, the researchers assessed blood samples from 51 pregnant individuals, and showed that their method can reveal genetic variants in the mother, as well as variants in the fetus that are not found in the mother but which have been linked to the prenatal diagnosis of disease.
"Our study suggests that it is feasible to screen most genes across the fetal genome using a blood test rather than requiring an invasive procedure such as amniocentesis," explained senior author Michael E. Talkowski, PhD, director of the Center for Genomic Medicine at Massachusetts General Hospital (MGH), among other appoinmtents.
There is an existing noninvasive screening method called prenatal-cell-free DNA-screening, and it can reveal the gain or loss of chromosomes, the number of X and Y chromosomes, Down syndrome (trisomy 21), and some fetal conditions. But many other diseases can only be identified if the parts of the genome that code for protein, known as the exome, are (is) analyzed. Exome screening for fetuses is challenging and expensive, however.
This new test, called non-invasive fetal sequencing (NIFS), could offer an alternative non-invasive method. Rgeardless of the amount of fetal DNA used in this approach, the researchers could find changes to DNA at the single-base level, even when they were not present in the matronal genome.
"The clinical implications of this research are potentially profound, particularly for pregnancies in which a fetal anomaly is suspected from ultrasound and an invasive test is indicated," noted co-senior study author Kathryn Gray, MD, PhD, an obstetrician and clinical geneticist at Brigham and Women's Hospital.
"It has long been known that fetal sequence variants can be obtained from cell-free fetal DNA, and exome sequencing is already part of the standard-of-care, but it currently requires an invasive procedure," added Talkowski. "These results suggest that non-invasive sequencing can likely capture the same genetic information from the fetal exome that is already being obtained in the standard-of-care, but from a blood test alone without the invasive procedure."
More research will still be necessary to validate this procedure and develop it for use in the clinic, but these early results are promising.
Sources: Massachusetts General Hospital, New England Journal of Medicine
