A new blood test uses scraps of fetal DNA to piece together a prenatal diagnosis.
In January, the American College of Obstetricians and Gynecologists recommended that all pregnant women have access to Down’s syndrome screening, which in the past was advised only for women age 35 and older. But prenatal tests for Down’s syndrome and other genetic abnormalities can be problematic. Initial screening can be done with ultrasound or a blood test, but a definitive diagnosis requires more-invasive procedures: amniocentesis or chorionic villus sampling, both of which carry a small risk of causing miscarriage. What’s more, the screening tests have a 5 percent false-positive rate, which results in many unnecessary procedures. recommended that all pregnant women have access to Down’s syndrome screening, which in the past was advised only for women age 35 and older. But prenatal tests for Down’s syndrome and other genetic abnormalities can be problematic. Initial screening can be done with ultrasound or a blood test, but a definitive diagnosis requires more-invasive procedures: amniocentesis or chorionic villus sampling, both of which carry a small risk of causing miscarriage. What’s more, the screening tests have a 5 percent false-positive rate, which results in many unnecessary procedures.