(AGI) Rome, Nov. 20 - Embryos with a mix of normal and abnormalchromosomes implanted during in vitro fertilisation can developinto healthy newborns, a new study suggests. The so-calledmosaic embryos were previously thought to cause abortions, butthe study shows the existence of a self-correcting mechanism.The study, published in the New England Journal of Medicine,was carried out by Italian researchers. "For the first time,partially diseased embryos, called aneuploid mosaic embryos,have been implanted in the womb. We have shown that this canresult in normal pregnancies and healthy babies," said ErmannoGreco, author of the study who is director of the Centre ofmedicine and reproductive biology at the European Hospital inRome. "This discovery has a dual clinical significance.First of all, embryos with partially abnormal chromosomes areable to self-correct and, once implanted, healthy cells takeprecedence over the diseased. As a result, now that we can alsouse these 'abnormal' embryos, we can actually increase thecumulative success percentages of in vitro fertilisation." Oneof the possible consequences of the discovery is a decrease inthe need for ovarian stimulation. The pilot study detectedchromosomal mosaicism in nearly 5 percent of about 3,800embryos included in the survey. It was explained to the couplesthat these embryos also had a chance to develop normallybecause of the presence of normal cell lines. Moreover, embryohealth can be monitored during development by analysing themother's blood. Mosaic embryos were transferred into 18 womenfor whom IVF hadn't previously worked. From these, six healthychildren were born, five girls and one boy. The findingsunderline the importance of genetic screening beforeimplantation to avoid excluding embryos that appear unsuitable.With this technique, called preimplantation genetic screening(PGS), the entire genetic constitution can now be mapped andrather than just a few chromosomes, as happened in the past.The screening is carried out without any risk to the foetus.(AGI) . .