In order to select the best embryos, we culture embryos to the blastocyst stage (day 5 or day 6)
Embryos are cultured in the laboratory incubator until they reach the blastocyst stage (5 days after the egg collection day) and then the best embryo/embryos are transferred into the uterus. In certain selected cases such as good prognosis patients or patients wishing to have a single embryo transfer, this strategy offers higher pregnancy rates than cleavage-stage (day 3) embryo transfer. However, a day 5 blastocyst transfer is not suggested for everybody and in fact in some cases, a day 3 embryo transfer is more suitable for some women.
Blastocyst culture is also performed on Pre Implantation Genetic Testing (PGT) cases since the biopsy of the trophoectoderm cells of the day 5 blastocyst allow a better reading of the genetic tests, compared to the biopsy of 1-2 cells of a day 3 embryo. In addition, by allowing the embryos to reach the blastocyst stage prior to the biopsy, we ensure that only suitable embryos are biopsied rather than biopsying all the day 3 embryos, hence decreasing any unnecessary costs for the patients.
At Pedieos IVF Center we follow the American Society for Reproductive Medicine (ASRM) guidelines which can be found on the ASRM website.
Please read below the most important points outlined in the ASRM Practice Committee report 2013:
- In ‘‘good prognosis’’ patients, blastocyst transfer results in increased live-birth rates compared to transfer of equal numbers of cleavage-stage embryos. Transfer of multiple blastocysts results in a high multiple pregnancy rate.
- In ‘‘poor prognosis’’ patients, blastocyst transfer has not been shown to result in increased live-birth rates compared with cleavage-stage transfer; however, in these populations there is a higher risk of day 3 embryos not progressing to the day 5 blastocyst stage, resulting in fewer or no embryos available for transfer.
- Extended culture leads to freezing only the good quality embryos that reach the day 5 blastocyst stage, as these embryos have an increased potential of implanting and developing.
- Day 5 Blastocyst culture may be associated with a small increased risk of adverse neonatal outcomes, but no causal relationship has been proven.
Please note that:
- “Good prognosis” patients are defined as patients ≤35 years with ≥10 follicles ≥12mm on the day of hCG injection, normal follicle-stimulating hormone (FSH) and E2 levels, no more than one previous unsuccessful cycle of in vitro fertilization (IVF)–embryo transfer, and good embryo quality.
- “Poor prognosis” patients are defined as patients >35 years with previous unsuccessful cycle of IVF/embryo transfer, elevated day 3 FSH levels and average to bad embryo quality.