Department of Reproductive Medicine, King Edward Memorial Hospital, Subiaco, Australia.
City Fertility Australia, Claremont, Australia.
Hum Reprod. 2023 Sep 5;38(9):1714-1722. doi: 10.1093/humrep/dead137.
Does the meteorological season at the time of oocyte retrieval affect live birth rates in subsequent frozen embryo transfers?
Frozen embryo transfers resulting from oocytes retrieved in summer have 30% increased odds of live birth compared to frozen embryo transfers resulting from oocytes retrieved in autumn, regardless of the season at the time of embryo transfer.
Season at the time of frozen embryo transfer does not appear to be associated with live birth rate. One study in the northern hemisphere found increased odds of live birth with frozen embryo transfer resulting from oocytes collected in summer when compared to those collected in winter.
STUDY DESIGN, SIZE, DURATION: Retrospective cohort study including all frozen embryo transfers performed by a single clinic over eight years, from January 2013 to December 2021. There were 3659 frozen embryo transfers with embryos generated from 2155 IVF cycles in 1835 patients. Outcome data were missing for two embryo transfers, which were excluded from analysis. Outcomes were analysed by the season, temperatures, and measured duration of sunshine at the time of oocyte collection and at the time of frozen embryo transfer.
PARTICIPANTS/MATERIALS, SETTING, METHODS: There were no significant differences between patients with oocyte collection or embryo transfers in different seasons. Meteorological conditions on the day of oocyte collection and the day of frozen embryo transfer, and in the preceding 14- and 28-day periods, were collected including mean, minimum, and maximum temperatures, and recorded duration of sunshine hours. Clinical and embryological outcomes were analysed for their association with seasons, temperatures, and duration of sunshine with correction for repeated cycles per participant, age at the time of oocyte retrieval, and quadratic age.
Compared to frozen embryo transfers with oocyte retrieval dates in autumn, transfers with oocyte retrieval dates in summer had 30% increased odds of live birth (odds ratio (OR): 1.30, 95% CI: 1.04-1.62) which remained consistent after adjustment for season at the time of embryo transfer. A high duration of sunshine hours (in the top tertile) on the day of oocyte retrieval was associated with a 28% increase in odds of live birth compared to duration of sunshine hours in the lowest tertile (OR 1.28, 95% CI: 1.06-1.53). Temperature on the day of oocyte retrieval did not independently affect the odds of live birth. The odds of live birth were decreased by 18% when the minimum temperature on the day of embryo transfer was high, compared with low (OR: 0.82, 95% CI: 0.69-0.99), which was consistent after correction for the conditions at the time of oocyte retrieval.
LIMITATIONS, REASONS FOR CAUTION: This was a retrospective cohort study, however, all patients during the study period were included and data was missing for only two patients. Given the retrospective nature, causation is not proven and there are other factors that may affect live birth rates and for which we did not have data and were unable to adjust, including pollutants and behavioural factors. We were also not able to stratify results based on specific patient populations (such as poor- or hyper-responders) nor report the cumulative live birth rate per commenced cycle.
These findings may be particularly relevant for patients planning oocyte or embryo cryopreservation. Given the increasing utilization of cryopreservation, identification of factors that influence outcomes in subsequent frozen embryo transfers has implications for future therapeutic and management options. Further studies to clarify the physiology underlying the influence of sunshine hours or season on subsequent frozen embryo transfer outcomes are required, including identification of specific populations that may benefit from these factors.
STUDY FUNDING/COMPETING INTERESTS: No funding was provided for this study. S.L. has received educational travel assistance from Besins, Merck and Organon outside the submitted work. R.H. is National Medical Director of City Fertility and Medical Director of Fertility Specialists of Western Australia, has received honoraria from MSD, Merck Serono, Origio and Ferring outside the submitted work, and has equity interests in CHA SMG. C.R., M.W., and E.N. declare that they have no conflicts of interest.
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取卵时的气象季节是否会影响随后的冷冻胚胎移植的活产率？
与秋季取卵相比，夏季取卵的冷冻胚胎移植活产率增加 30%，无论胚胎移植时的季节如何。
冷冻胚胎移植时的季节似乎与活产率无关。一项在北半球进行的研究发现，与冬季相比，夏季取卵的冷冻胚胎移植活产率增加，而冬季取卵的冷冻胚胎移植活产率增加。
研究设计、大小、持续时间：这是一项回顾性队列研究，包括一家诊所在八年期间进行的所有冷冻胚胎移植，从 2013 年 1 月至 2021 年 12 月。共有 3659 例冷冻胚胎移植，涉及 1835 名患者的 2155 个 IVF 周期。由于两个胚胎移植的结果数据缺失，因此将其排除在分析之外。通过取卵时和冷冻胚胎移植时的季节、温度以及阳光持续时间的测量来分析结果。
参与者/材料、设置、方法：在不同季节，取卵和胚胎移植的患者之间没有显著差异。收集取卵日和冷冻胚胎移植日以及前 14 天和 28 天期间的气象条件，包括平均、最低和最高温度，以及记录的阳光持续时间小时数。分析临床和胚胎学结果与季节、温度和阳光持续时间的关系，并对每个参与者的重复周期、取卵时的年龄和二次年龄进行校正。
与秋季取卵的冷冻胚胎移植相比，夏季取卵的冷冻胚胎移植活产率增加 30%（优势比[OR]：1.30，95%CI：1.04-1.62），在调整胚胎移植时的季节后仍然一致。取卵日阳光持续时间较长（在前三分之一）与阳光持续时间较低的情况相比，活产率增加 28%（OR 1.28，95%CI：1.06-1.53）。取卵日的温度并不能独立影响活产率。与低温相比，当胚胎移植日的最低温度较高时，活产率降低 18%（OR：0.82，95%CI：0.69-0.99），这在调整取卵时的条件后仍然一致。
局限性、谨慎的原因：这是一项回顾性队列研究，但是在研究期间所有患者都被纳入，只有两名患者的数据缺失。鉴于回顾性研究的性质，不能证明因果关系，而且还有其他可能影响活产率的因素，而我们没有这些数据，也无法调整，包括污染物和行为因素。我们也无法根据特定的患者群体（如低反应者或高反应者）对结果进行分层，也无法报告每个启动周期的累积活产率。
这些发现可能对计划取卵或胚胎冷冻保存的患者特别相关。鉴于冷冻保存的使用日益增加，确定影响随后冷冻胚胎移植结果的因素对未来的治疗和管理选择具有重要意义。需要进一步研究以阐明阳光持续时间或季节对随后的冷冻胚胎移植结果的影响的生理学基础，包括确定可能受益于这些因素的特定人群。
研究资金/利益冲突：本研究没有提供资金。S.L. 从 Besins、Merck 和 Organon 获得了与提交工作无关的教育旅行援助。R.H. 是 City Fertility 的国家医疗主任和 Fertility Specialists of Western Australia 的医疗主任，从 MSD、Merck Serono、Origio 和 Ferring 获得了与提交工作无关的酬金，并在 CHA SMG 拥有股权。C.R.、M.W. 和 E.N. 声明他们没有利益冲突。
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