In the past, when undergoing In Vitro Fertilization (IVF) procedures, embryos have been transferred into the uterus at the 4-8 cell developmental stage. This usually occurred two to three days following the egg retrieval. Clinical data has shown that by culturing embryos for an additional two to three days (to allow them to develop to the blastocyst stage), pregnancy rates per embryo transferred may be increased. Because of this improvement, fewer embryos can be transferred resulting in lower rates of high-risk multiple pregnancies.
Given the benefit of this technique, the ART Program feels it is in the best interest of patients to pursue this opportunity.
Once initial fertilization has been assessed, patients will be counseled regarding management of their embryo transfer. Due to increased multiple gestation rates, it is recommended that only one or two blastocysts be transferred to women less than age 35 or to women receiving donated oocytes, two blastocysts to women age 35-37, three blastocysts to women age 38-40 and up to four blastocysts to women over age 40. Additional blastocysts only slightly increase the pregnancy rate and greatly increase the risk for a high-risk multiple gestation. For patients with the most favorable prognosis, consideration should be given to the single embryo transfer option.
Please be advised that a small percentage of patients may not produce any blastocysts from their cycle. However, embryos of lower developmental stage can be transferred. A lower pregnancy rate would be expected. It is not known if transfer of their embryos at an earlier time would have resulted in the same pregnancy rate due to the poor quality of their embryos, but it is valuable to understand the embryo development impact on future pregnancy rates in your IVF cycles.
On average, approximately 40-50% of all fertilized eggs will develop to the blastocyst stage in culture. If desired, good quality blastocysts achieved in excess of those transferred may be cryopreserved for later use. On average, approximately 15-20% of all fertilized eggs cultured for possible cryopreservation will develop into a good quality blastocyst and be cryopreserved.