Blood Test Detects Abnormalities in Developing Fetus

A cheap, simple, noninvasive blood test may replace invasive diagnostic techniques in early pregnancy.

Dutch scientists are developing a prenatal blood test that would be able to detect accurately chromosomal abnormalities in the developing fetus. At present, the only reliable way to do this is through amniocentesis or chorionic villus sampling, which is invasive and carries the risk of triggering a miscarriage.

Dr. Suzanna Frints, a clinical geneticist at Maastricht University Medical Center (Maastricht, The Netherlands) and colleagues have been able to use molecular-genetics probes to detect DNA belonging to the fetus in blood samples taken from pregnant women.

The team used the Multiplex Ligation-dependent Probe Amplification (MLPA), technique to detect fetal DNA that is present in the blood of women who have been pregnant for at least six to eight weeks. The MLPA test is part of an existing kit that is already used around the world to detect chromosomal abnormalities in invasively obtained amniotic fluid or chorionic villi samples from pregnant women.

The kit is cheap and fast, delivering results within 24-62 hours, but until now, it has only been used on samples taken during invasive procedures; it was not known whether it would work on cell free fetal DNA circulating in blood samples of pregnant women.

The scientists have been successful in identifying DNA from the Y chromosome, indicating that the fetus is a boy and could be at risk of inheriting an X-linked disorder such as Duchenne's muscular dystrophy and hemophilia.

The scientists believe the same method can be used to detect trisomy 21 (where an extra chromosome 21 causes Down's syndrome) and they are investigating this next, followed by trisomy 13 and 18 (responsible for causing Patau and Edward's syndromes respectively).

Dr. Frints said, "At the moment, the reliability of the test is about 80% due to false negative results, but we are working to improve the accuracy of the MLPA probe . Although we need to test and refine this MLPA technique further, our results so far are promising."

The work was presented at the 26th annual meeting of the European Society of Human Reproduction and Embryology in Rome (Italy) on June 29, 2010.

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Maastricht University Medical Center