Although advances in in vitro fertilization (IVF) testing have improved outcomes for couples with infertility, these advances have spurred debate over “mosaic” embryos—embryos with both normal and abnormal cells. One such advanced method, preimplantation genetic screening (PGS), takes a biopsy of just a handful of cells from the outside of the embryo and then classifies them as normal or abnormal.

There is debate in the field of fertility over whether mosaic embryos should be implanted. “Mosaic embryos are not abnormal embryos. Abnormal embryos don’t make babies or pregnancies,” says James A. Grifo, MD, professor in the Department of Obstetrics and Gynecology. “Mosaic embryos have potential. They don’t have the same potential as a chromosomally normal embryo, but they can make babies,” he tells CBS This Morning.

Dr. Grifo, who is also the director of NYU Langone’s Fertility Center and Division of Reproductive Endocrinology and Infertility, warns that mosaic embryos carry a higher risk of miscarriage, and more research is needed to better understand mosaicism.

Read and watch more on CBS This Morning.