A worldwide study that is led by Texas Fertility Center, an Austin, TX, fertility clinic, and includes top fertility clinics in the United States, Spain, Israel, France, Japan and the Netherlands, has the goal of dramatically changing how scientists determine embryo viability for in vitro fertilization (IVF).
Typically during IVF, the embryologists in the lab select the embryos to transfer to the uterus via a method called embryo grading. This is a subjective system based on the appearance of the embryo under the microscope. For example, with a Day 3 embryo, a Grade 1 embryo might have cells of equal size and no fragmentation (when a small portion of the cytoplasm inside the cell breaks off) compared to a Grade 4 embryo with cells of unequal size and moderate to heavy fragmentation. There are different grading systems for Day 5 (blastocyst) embryos.
Embryo grading is an imperfect tool to determine which embryos have the best potential for a healthy pregnancy and birth. The technique has limited ability to determine which embryos are most likely to implant because at least 60 percent of human embryos that may appear normal under a microscope are actually chromosomally abnormal and are likely to not implant or miscarry.
