The debate over cleavage stage (day 3) versus blastocyst stage (day 5/6) transfer continues to rage on in the reproductive community. Transferring embryos at the blastocyst stage has many recognized, albeit theoretical, advantages. These include higher implantation rates, selection of the most viable embryo, reduced number of embryos needed for transfer, and better synchronization between the embryo and endometrial lining at transfer. However, this is such a debated topic that recently the Practice Committee for the American Society for Reproductive Medicine (ASRM) put together an opinion on blastocyst culture and transfer. Since we get a lot of questions regarding day 3 vs. blastocyst transfer, I have summarized the ASRM committee’s recent opinion, as published in Fertility and Sterility, March 2013, so that you may be more informed when it comes to your embryo transfer.
- Reliable criteria to identify embryos destined to develop into blastocysts are not currently established. At this time, the only way to predict which embryos will develop into a viable blastocyst, is to culture to the blastocyst stage.
- In “good prognosis patients” (see paragraph below for explanation) blastocyst culture has been shown to improve live birth rates compared to the transfer of cleavage stage embryos.
- Implantation rates have been shown to be higher in blastocyst transfers; therefore “good prognosis” patients wishing to have only a singleton pregnancy should be advised to transfer only one blastocyst.
- There may be a small increased risk of monozygotic twinning with blastocyst transfer as compared to cleavage stage transfer, however studies have yet to conclusively confirm that correlation.
- In “poor prognosis” patients (see paragraph below for explanation), blastocyst transfer has not shown an increase in live birth rates as compared to day 2 or day 3 transfers, however, it does give some predictive information about the quality of the embryos and their ability to develop into viable blastocysts. Pregnancy rates between day 3 and day 5/6 embryo transfers in “poor prognosis” patients are not significantly different.
- Blastocyst transfer may slightly increase the likelihood of conceiving a male child, but only if the mode of fertilization was natural insemination. If ICSI was used as the mode of fertilization, no increase was seen.
- Blastocyst development varies greatly among patients, ranging from 0% development to 100% development, with typical “usable” blastocyst formation rates of about 40%.
- Extended culture leads to fewer embryos to cryopreserve, however, a good blastocyst cryopreservation program in the laboratory leads to higher survival rates with the blastocysts that are frozen.
In our practice, the decision between cleavage or blastocyst stage transfer depends on many factors. Our "good prognosis" patients, those defined as less than 35 years of age, good antral follicle counts, AMH and FSH levels within normal limits, and a predicted good response to gonadotropins, are routinely taken out for blastocyst transfer. We also take patients who may be considered “poor prognosis” to the blastocyst stage to assess viability and embryo competence, especially if they have already failed a day 2 or day 3 transfer.
The debate over optimal transfer day will continue on, but at InVia Fertility Specialists, we will continue to consider all factors of your cycle and do what is best for you to achieve a viable pregnancy.
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