Not so long ago, IVF focused primarily on the transfer of fresh embryos. Frozen embryos were considered "surplus embryos." They were assessed by the embryologist as having sufficient potential to merit freezing for possible future use but not quite as much potential as the embryos chosen for fresh transfer. In the last few years, the focus of IVF in many research-oriented, cutting-edge fertility clinics has reversed to the transfer of frozen embryos.
Why? Some reasons include:
1. Advances made in vitrification (freezing) techniques, which permit excellent IVF success rates with embryos that have been frozen and then thawed;
2. The increasing popularity of pre-implantation genetic screening (PGS), which often involves the freezing and thawing of embryos, to identify chromosomally normal embryos for transfer into the woman's uterus;
3. The increasing popularity of "embryo banking," where a woman who produces few embryos in a single IVF treatment cycle opts to undergo additional stimulations and retrievals to create and batch more embryos for biopsy and PGS analysis; and
4. Recent research suggesting that embryos are more likely to implant if transferred into the uterus in a cycle after the one in which the woman's ovaries were stimulated and when the uterus has recovered from the effects of the ovarian stimulation drugs. This research has influenced some fertility clinics to freeze and then thaw embryos even when the patient does not intend to pursue PGS.
Success rates for IVF are compiled and published annually by the Society for Assisted Reproductive Technology (SART) and by the Centers for Disease Control (CDC). These publications were made available in response to a congressional act that recognized that public access to fertility clinic success rates would provide an element of "consumer protection." Because the format of these fertility clinic success rate reports was designed when fresh embryo transfers were the primary focus of IVF, patients must be careful to avoid interpreting them based on old assumptions that no longer apply.
In light of this, here are a number of factors patients need to be aware of when interpreting fertility clinic IVF success rate reports in their current format:
1. The reporting rules allow clinics to exclude embryo banking cycles from their fresh embryo success rates, because these cycles are not intended to produce an immediate outcome;
2. Embryo banking cycles will appear in a clinic's frozen embryo IVF success rates, but only if at least one embryo is identified as chromosomally normal via PGS and then transferred. Clinic data won’t indicate that the woman participated in multiple stimulations;
3. In clinics that perform a lot of embryo banking cycles, cycles reported in the fresh embryo category tend to involve patients with a better prognosis, where their fresh, untested embryos have good odds of implanting;
4. In most clinics, embryos are frozen while PGS analysis is being performed. Embryos identified as chromosomally normal are then thawed and transferred in a subsequent menstrual cycle. The outcomes of these transfers appear in the clinic's frozen embryo success rates;
5. In some fertility clinics, when circumstances permit, PGS analysis is conducted within 24 hours. Embryos identified as chromosomally normal can be transferred “fresh” in the same treatment cycle. The outcomes of these transfers appear in the clinic's fresh embryo success rates; and
6. Some clinics still use PGS infrequently and transfer mostly unscreened, fresh embryos. In these clinics, an outcome is reported for all cycles, including those involving women who produce more abnormal than normal embryos. When these clinics freeze, thaw, and then transfer embryos, they tend to be "surplus embryos" that have not been subjected to PGS analysis. These clinics will then show a lower IVF success rate compared to others that perform PGS.
When looking at a clinic's success rate report, it would be ideal if the patient could understand her statistical probability of being able to have a baby using the various treatment approaches she may be considering. However, with different types of IVF cycles lumped together, it is impossible for the patient to identify the process that was engaged in for each cycle reported. Unfortunately, in their current formats, the SART Registry and the CDC Reports do not allow patients to develop the insights and gain the protection they were originally intended to provide.
SART has acknowledged that changes to the reporting structure are necessary to address the introduction of new approaches to IVF. These changes will be introduced to the public in 2016 beginning with treatments that occur in this calendar year. However, a lingering question remains: Is IVF technology now so complex that it has become impossible to present fertility clinic IVF success rates in a format that will be interpretable by patients and satisfy the consumer protection objective they were originally intended to provide?
You can visit Ms. Levy's blogs at http://empoweredivf.com/blog/ and at http://www.fertilityauthority.com/content/own-the-process-empowered-ivf
Editor’s Note: Univfy IVF Prediction Tests provide personalized predictions of IVF success rates. With both the Univfy PreIVF and Univfy PredictIVF, we show the live birth probability based on using fresh and any frozen embryos that resulted from one IVF cycle, as defined by one cycle of ovarian stimulation with IVF drugs, plus egg retrieval and embryo culture. The live birth probability reported by Univfy IVF Prediction Tests is not affected by whether the patient opts for PGS or uses fresh or frozen embryos.