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"The healthy development of an embryo created through in vitro fertilization (IVF) depends on whether most, if not all, of the cells have the proper number of chromosomes. With pre-implantation genetic screening (PGS) technology, doctors can, in principle, spot-check chromosome count before choosing which embryo to implant in the mother. In a new article, however, scholars at Brown University and the University of Washington report that PGS has serious limitations that can only be overcome with more human embryo research, even as they acknowledge the controversy surrounding that research.
What doctors and hopeful parents want to see in PGS is 46 chromosomes -- two pairs of 23 -- a normal state of affairs called "euploidy." An abnormal number, or "aneuploidy," could signal a fatal flaw in early development. In 2013 in the United States, more than 15 percent of IVF pregnancies ended in miscarriage, often because of aneuploidy, wrote Dr. Eli Adashi, professor of medical science and former dean of medicine and biological sciences at Brown, and Rajiv McCoy, a genome sciences postdoctoral fellow at Washington. The miscarriage rate rises quickly with maternal age, as does the rate of aneuploidy.
Hoping to prevent a bitter loss, a growing percentage of infertility patients using IVF have turned to PGS. But as Adashi and McCoy wrote in the journal EMBO Reports, PGS has yielded mixed results. Sometimes it has predicted the doom of embryos that became healthy children, and in the small studies conducted so far, there has been mixed evidence that its use leads to a greater likelihood of a successful pregnancy.
"The impact of PGS on the outcome of assisted reproduction remains uncertain," they wrote..."
