Non-invasive identification of foetal Down's syndrome

A test for foetal Down's syndrome that does not involve taking samples from either the placenta or the amniotic fluid has been developed by scientists from the Chinese University of Hong Kong.

The technique, which will be described in 25 November Lancet, detects the foetal genetic abnormalities associated with Down's syndrome in maternal plasma. In preliminary tests, YM Dennis Lo and colleagues used fluorescence in situ hybridisation (FISH) on maternal plasma samples from three women carrying foetuses affected by trisomy 21 (Down's syndrome). The technique identified foetal cells with three chromosome-21 signals — the genetic markers for the disease — in the mothers' plasma.

Although further large-scale trials are necessary, the authors hope that the FISH technique could offer a safer alternative to amniocentesis. "Ultimately, with further technical refinements, prenatal diagnosis by maternal plasma DNA analysis could reduce our reliance on invasive methods, leading to safer investigative protocols." The FISH ...