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| |  Safe Alternative To Amniocentesis? LONDON -- August 15, 1997 -- In The Lancet this week, Dr. Y. M. Dennis Lo and colleagues from the United Kingdom and Italy report that DNA from a fetus in the womb is present in the blood of the pregnant mother, which could enable physicians to make safer and quicker prenatal diagnoses. The passage of nucleated blood cells between mother and fetus has been recognised. An important application is the use of fetal cells in maternal blood for non-invasive prenatal diagnoses, thereby avoiding conventional invasive techniques (such as amniocentesis and chorionic-villus sampling), which carry greater risks. Although advances have been made in techniques that use maternal blood, such techniques remain time-consuming and expensive. Prompted by reports that tumour DNA has been found in the plasma and serum of cancer patients, the researchers extracted DNA from plasma and serum and nucleated blood cells from 43 pregnant women carrying male fetuses so that circulating male fetal DNA could be detected. Fetus-derived Y-chromosome sequences were detected in 24 (80 percent) of the 30 maternal plasma samples, and in 21 (70 percent) of the 30 maternal serum samples, from women bearing male fetuses. These results were obtained from just 10 µL of the samples. But when DNA from nucleated blood cells extracted from a similar volume of blood was used, only five (17 percent) of the 30 samples gave a positive Y result. None of the women bearing female fetuses, and none of the non-pregnant control women, had positive results for plasma, serum, or nucleated blood cells. “As well as sex-linked disorders,” conclude Dr Y M Dennis Lo and colleagues, “techniques for fetal-DNA detection in maternal plasma and serum can also be used to detect many paternally inherited DNA sequences that differ from their maternal counterparts.” The approach might also be useful in screening for genetic abnormality (including that which results in Down’s syndrome), and for “improving our understanding of the fetomaternal relationships” in general.
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