Bioethics Blogs

Questions About Using “Mosaic” Embryos in IVF

Couples undergoing IVF routinely undergo preimplantation genetic screening, or PGS, to make sure that their embryos are viable and free of genetic disease. However, some embryos have both normal and abnormal cells, and at least some of these “mosaic” embryos are capable of developing into healthy children, as described in a New York Times article. This raises a troubling question: should mosaic embryos be used to create a pregnancy? Fertility specialists are divided on the issue.

In part, the disagreement rests on factual questions regarding the reliability of PGS screening. Dr. Norbert Gleicher questions “whether a biopsy that examines five to ten random cells from the outer shell of a 200-cell embryo can reliably represent the inner cell mass, the crucial core from which the fetus develops.” He reports three normal births after the transfer of mosaic embryos. But Dr. Mark Sauer responds that such a small sample of healthy babies does not warrant a change in the standard practice not to implant mosaic embryos, especially since problems may show up later in childhood or adulthood.

If the only risk is that the embryo won’t implant, and the woman will miscarry, it seems reasonable to allow infertility patients to decide whether to take that risk. But what if there is a serious risk that the child will have developmental defects? Is that a risk that prospective parents should be able to take? Should physicians accede to such a request?

The question is complicated by the fact that, quite apart from the factual issues about the reliability of PGS, there’s another deeper, conceptual question: May prospective parents take risks with the health of their future child if there is no other way that the child can be born?

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.