Q: Why have live-birth rates on SART appeared to be focused on “per IVF cycle” as opposed to the CDC reporting of live births “per embryo transfer?”
A: An ART cycle “start” is defined as the initiation of ovarian stimulation with medication that may or may not include administration of exogenous gonadotropins, followed by oocyte retrieval and embryo transfer. Not every patient beginning a cycle will undergo an oocyte retrieval and not all patients who undergo oocyte retrieval have an embryo transfer. The live-birth rates (LBR) for each of these steps of progression in the ART process are available in the SART and CDC reports.
In 2016, SART recognized that practices were foregoing fresh embryo transfer after oocyte retrieval, opting to cryopreserve all embryos to either accommodate genetic testing of the embryos prior to transfer or to avoid embryo transfer to an unfavorable uterine environment. In response to changes in practice and in an effort to deemphasize live birth per transfer, thereby alleviating a potential motivator or pressure for practitioners to transfer multiple embryos, SART moved to a report that displays the cumulative live-birth rate per cycle start for oocyte retrieval. The cumulative live-birth rate per cycle start for oocyte retrieval is the chance of live birth from transfers of embryos derived from the oocyte retrieval and performed within 1 year of the oocyte retrieval.
This change in reporting further reduced the pressure to transfer multiple embryos and encouraged elective, single-embryo transfer. The outcome per transfer is no longer the report’s primary focus.
Q: The latest pregnancy outcomes statistics are from the year 2020 and are finalized by the CDC. Why does the SART website have this same year labeled “preliminary” outcomes?
A: Shortly after the 2016 SART report change, the CDC made similar changes to their report. The difference is that SART provides a “preliminary” report of outcomes within the year of the cycle start for oocyte retrieval. The cumulative outcome is not “finalized” until the following year as transfers may be performed as late as 12 months after the oocyte retrieval.
SART has opted to report both the “preliminary” or interim outcome and the “final” outcome a year later. The CDC has opted to limit their report to “final” outcomes. I’m happy to report that SART recently released the final report for 2021 cycles.
Q: Have national success rates in the United States continued to rise or have they plateaued?
A: It appears that success rates have plateaued; however, we find ourselves at another point where practice patterns and patients’ approach to using ART for family building have changed.
Recognizing the impact of maternal aging on reproductive potential, patients are opting to undergo multiple ART cycles to cryopreserve embryos for family building before they attempt to get pregnant. This family-building path reduces the value of measuring the LBR per cycle start as we may not know the outcome for many years. SART leaders are deliberating intently as to how to best represent this growing patient population in outcome reporting.