A: According to Dr. Desireé McCarthy-Keith the ability to culture embryos to the blastocyst stage (day 5) has been a major advance in IVF. Culturing embryos beyond day 3 allows a sort of natural selection to take place, where the most robust embryos will continue to develop and others may arrest. Our embryologists are then able to transfer embryos which are more likely to implant and lead to a pregnancy. Further, when we can more confidently determine which embryos are the best, we are able to transfer fewer embryos at a time which reduces the risk of multiple births. Embryos may be transferred on day three if there are fewer embryos developing, but culture to day 5 is preferred.
Dr. Desireé McCarthy-Keith is a Board Certified reproductive endocrinologist with Georgia Reproductive Specialists, and a Clinical Professor of obstetrics and gynecology at Morehouse School of Medicine. For more information on this topic, listen to the Creating a Family radio show: IVF Transfers: Fresh vs. Frozen; 3 day vs. 5 day
Image Credit: Christina