A developing baby's entire genome is hidden in its mother's blood, potentially offering a non-invasive test for congenital diseases. Dennis Lo of the Chinese University of Hong Kong and his colleagues sequenced billions of DNA base pairs from the plasma of a pregnant woman and then developed a way to distinguish her DNA sequences from the fetus's.

Both parents carried a single mutation for β-thalassaemia, a rare blood disorder caused by two faulty copies of the gene HBB. Lo's analysis demonstrated that the father had passed on his mutation, but the mother had given the fetus a healthy copy of HBB, sparing it from β-thalassaemia. Such genetic screening could replace invasive prenatal diagnostic tests such as amniocentesis.

Sci. Transl. Med. 2, 61ra91 (2010)