WHAT IS A BLASTOCYST

A blastocyst is an embryo with two cell types: the trophectoderm, or outer layer, which may eventually become the placenta, and the inner cell mass that may differentiate into the fetus. Blastocysts usually form by day 5-6 after retrieval.

PATIENTS WHO WILL BENEFIT FROM BLASTOCYST TRANSFER

Patients with many good quality cleaved embryos on day 3 benefit from culture of embryos for 2 additional days and transfer of blastocysts on day 5.  The extra 2 days in culture gives additional information about embryo quality which improves our ability to identify the embryos that are most likely to implant when transferred to the uterus.  This results in a higher implantation rate.  Because of the higher implantation rate, fewer blastocysts need to be transferred, leading to a lower incidence of multiple births.  However, blastocyst transfer is not a good idea for everyone.  If a couple has a low number of embryos, the extended culture may not result in development of any blastocysts.  If this were to happen, no transfer would be performed.  In these cases it is much better to transfer the embryos to the uterus on day 3. 

TRANSFER OF A SINGLE BLASTOCYST RESULTS IN A GOOD PREGNANCY RATE AND A LOW MULTIPLE RATE

BRM STATISTICS 2007-2011