Pre-implantation Genetic Screening for planned Single Embryo Transfers

Recent advances in the technology for testing embryos has allowed top clinics to move away from day 3 (multicellular) embryo biopsies to biopsies on the 5th and 6th day of embryo culture. As a result, the face of in vitro fertilization (IVF) is changing.

Having performed pre-implantation genetic screening (PGS) and pre-implantation genetic diagnosis (PGD) since 1999, I have witnessed the evolution of the technology for testing the cells submitted, and recently have seen changes in the developmental stage at which embryos are tested.

In the past, many PGS/PGD programsincluding oursdepended on the data gained from sampling a six to eight celled embryo. The data was useful and reliable enough to prevent genetic diseases and helped us better choose embryos, but the information was never robust enough so that almost all embryo transfers could be single embryos. Unfortunately, we continued to implant two or three embryos for many years. As a result, there were many multiple pregnancies.

Twin and higher order pregnancies, as well as the associated morbidity connected with pre-term birth, have been the main complication of assisted reproductive techniques.  IVF centers were looking for a way to get such reliable information about embryos that almost every IVF could conclude with a single embryo transfer and result in pregnancy at at high rate (excess of 75 percent) regardless of the age of the patient.

Recent publications and our own experience are showing us that the information from blastocyst laser assisted biopsies of the trophectoderm give such accurate information about the number of chromosomes in embryos that single embryo transfers have become the rule and not the exception. Scientific reports of single "euploid" embryo transfers have shown pregnancy rates in excess of 65 percent, while our own experience exceeds this.  What is remarkable is that top clinics may have reached the pinnacle of assisted reproductive medicine if almost all treatments can be completed without the most common and feared complication.