Amniocentesis and other prenatal tests designed to assess fetal health carry a small risk of miscarriage. Now Chinese researchers may have found an alternative diagnostic method based on a technique that distinguishes maternal DNA from fetal DNA in the mother's blood. That ability could lead to simple, no-risk blood tests that determine whether a fetus has a problem caused by single-gene mutations, such as cystic fibrosis and sickle cell anemia. The fetal DNA, which tends to be shorter than that of the mother, is duplicated and subjected to a “molecular counting” technique that tallies both mutant and normal genetic material. Researchers can use the data to determine whether the fetus has inherited a monogenetic disease. The San Diego–based biotech company Sequenom plans to develop the test for commercial distribution. The study appears in the December 16, 2008, Proceedings of the National Academy of Sciences USA.