19EMBRYOS-superJumbo“The couple wanted a baby boy, but the male embryo they had chosen — the only one available after an expensive round of in vitro fertilization — received a troubling test result.

A handful of cells from the five-day-old embryo were deemed abnormal, apparently missing Chromosome 21, an absence that can lead to developmental defects.

Many couples having IVF would have reconsidered their choices. But the two women, aged 48 and 45, had the embryo implanted anyway. And despite the initial test findings, their baby was born healthy in 2014.”

According to a newer high-resolution, next-generation pre-implantation genetic screenings (P.G.S.) only recently available in the IVF process, “about 20 percent of embryos have both normal and abnormal cells, and the percentage increases with maternal age. These so-called mosaic embryos have long been known, but they have been detectable during an active IVF cycle only in the last year.”

Many IVF doctors are reluctant to implant these mosaic embryos, concerned about failure to implant, the risk of miscarriage, or the birth of a child with serious birth defects. Still others are cautiously proceeding if the patient has no normal embryos available and submits to genetic counseling first. P.G.S. is still advancing and being studied for its accuracy and reliability.

“Dr. Santiago Munné, director of Reprogenetics, a P.G.S. lab, applauded the advanced technology for discerning mosaicism even as it raises clinical quandaries.

“I think it’s a good thing we know now there is a third category, so we’re not going to discard any embryo that has even a little chance of implanting,” he said.”