But the new study also shows the limitations of transferring such embryos. A vast majority of the 144 embryos transferred by the group had only one or two chromosomal abnormalities, but the transfers resulted in 11 miscarriages in addition to the eight live births.
“There are a lot of miscarriages in that ratio,” said Laura Hercher, director of student research for the Sarah Lawrence College Genetic Counseling Program.
The PGT-A test is used to screen for aneuploidy, which is when an incorrect number of chromosomes — either too few or too many — is detected in sampled cells. An abnormal number of chromosomes can lead to genetic disabilities, such as Down syndrome, in severe cases. More often, the wrong number of chromosomes can lead to failed pregnancies, either by preventing embryos from being implanted or by causing miscarriages.
But the problem with PGT-A, the study authors argue, is that it provides an incomplete picture that is often interpreted as a very definitive result. The test is based on taking a handful of cells from the outer shell of the developing embryo and testing to see if each of them has 23 pairs of chromosomes.
“The goal of PGT was to select embryos that would give someone a better chance of conceiving,” says Dr. David Barad, an OB-GYN at the Center for Human Reproduction and a co-author of the study. “But genetic testing doesn’t make embryos better, it just gives us an idea of who they are.”
While continuing to use these embryos with abnormalities may carry some risk, authors of the new study, who were all affiliated with the clinic that performed the transfers, claim that: viable embryos are currently being ignored, leading many women to believe they have no other options for getting pregnant.
“The miscarriage rate is about what you would expect at such an advanced age,” said Dr. Norbert Gleicher, director of the clinic and a co-author of the study, by email. He added: “Ask women what they prefer. A risk of miscarriage or no chance of having a baby at all. The answer will be obvious.”
