STUDY QUESTION Using time-lapse data, can the current consensus for the timing of fertilisation assessment of oocytes, cultured in standard incubation, be optimised? SUMMARY ANSWER The optimum time to perform fertilisation assessment for oocytes cultured in standard incubation is 16.5 ± 0.5 h post-insemination (hpi), and the current consensus requires modification in order to minimise the chance of fertilisation being missed. WHAT IS KNOWN ALREADY Time-lapse incubation allows the embryologist to retrospectively review collated images of oocytes and embryos to capture important embryological observations that may otherwise be missed in standard incubation. According to expert consensus, the optimum time to perform the assessment of fertilisation is 17 ± 1 hpi. STUDY DESIGN, SIZE, DURATION A retrospective, multicentre analysis utilised data obtained from 54 746 ICSI-derived embryos and 23 602 IVF-derived embryos cultured in time-lapse incubation between January 2011 and November 2019. PARTICIPANTS/MATERIALS, SETTING, METHODS Using time-lapse imaging (TLI), the precise time of pronuclei appearance and disappearance was recorded, where applicable, and the number of oocytes with two pronuclei observable during 10 30-min intervals from 15 hpi to 20 hpi was determined. MAIN RESULTS AND THE ROLE OF CHANCE Between 15 and 17.5 hpi, the average number of oocytes exhibiting normal fertilisation, elicited as two pronuclei, was 98.19% with the highest proportion of oocytes having visible pronuclei at 16–16.5 hpi (98.32%). At 18–18.5 hpi, the number of visible pronuclei reduced to 95.53% and continued to fall to 87.02% at 19.5–20 hpi. LIMITATIONS, REASONS FOR CAUTION The authors’ expectation is that these findings are transferable to other settings, however it is possible that, with alternative culture media and incubation environments, calibration of this timing may be required. As data cannot readily be recorded for pronuclear appearance for IVF-derived embryos, it is not possible to determine the optimum time to perform the fertilisation assessment for IVF-derived embryos. WIDER IMPLICATIONS OF THE FINDINGS By fine-tuning the time at which fertilisation assessment takes place the accuracy of the assessment can be increased to maximise the number of fertilised oocytes identified, thereby increasing the number of usable embryos for the patient. Without TLI and following current consensus guidelines, over 11% (n = 3000) of oocytes would have been marked as unfertilised within this cohort. Further to this, depending on the time of a standard fertilisation assessment, up to 300 embryos which resulted in live births could have been categorised as unfertilised, as they presented no visible pronuclei at the conventional assessment time-point. STUDY FUNDING/COMPETING INTEREST(S) A.C. is a minor shareholder in CARE Fertility Limited. Validated algorithmic time-lapse embryo selection is offered to patients at CARE Fertility at an additional charge as an adjuvant treatment option. TRIAL REGISTRATION NUMBER N/A.

中文翻译：

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优化标准孵化中培养的卵母细胞的受精评估时机：从 78 348 个胚胎的延时成像中吸取的经验教训

研究问题 使用延时数据，可以优化目前对标准孵化培养的卵母细胞受精评估时间的共识吗？总结答案 对在标准孵化中培养的卵母细胞进行受精评估的最佳时间是授精后 16.5 ± 0.5 小时 (hpi)，目前的共识需要修改，以尽量减少错过受精的机会。已知情况 延时孵化允许胚胎学家回顾性地审查卵母细胞和胚胎的整理图像，以捕捉在标准孵化中可能会遗漏的重要胚胎学观察结果。根据专家共识，进行受精评估的最佳时间为 17 ± 1 hpi。研究设计、规模、持续时间回顾展，多中心分析利用了从 2011 年 1 月至 2019 年 11 月期间在延时孵化中培养的 54 746 个 ICSI 衍生胚胎和 23 602 个 IVF 衍生胚胎获得的数据。参与者/材料、设置、方法使用延时成像 (TLI)，精确在适用的情况下记录原核出现和消失的时间，并确定在从 15 hpi 到 20 hpi 的 10 个 30 分钟间隔内可观察到的具有两个原核的卵母细胞数量。主要结果和机会的作用 在 15 和 17.5 hpi 之间，表现出正常受精的卵母细胞的平均数量（作为两个原核诱发）为 98.19%，其中在 16-16.5 hpi 时具有可见原核的卵母细胞比例最高（98.32%）。在 18-18.5 hpi 时，可见原核的数量减少到 95.53%，并在 19.5-20 hpi 时继续下降到 87.02%。限制，谨慎的原因 作者的期望是这些发现可以转移到其他环境，但是，如果使用替代培养基和孵化环境，可能需要校准此时间。由于无法轻易记录 IVF 衍生胚胎的原核外观数据，因此无法确定对 IVF 衍生胚胎进行受精评估的最佳时间。研究结果的更广泛意义通过微调受精评估发生的时间，可以提高评估的准确性，以最大限度地识别受精卵母细胞的数量，从而增加患者可用胚胎的数量。如果没有 TLI 并遵循当前的共识指南，超过 11%（n = 3000）的卵母细胞将在该队列中被标记为未受精。此外，根据标准受精评估的时间，多达 300 个导致活产的胚胎可能被归类为未受精，因为它们在常规评估时间点没有可见的原核。研究资金/竞争利益 AC 是 CARE Fertility Limited 的小股东。CARE Fertility 向患者提供经过验证的算法延时胚胎选择，作为辅助治疗选择，需额外付费。试用注册号 不适用。是CARE Fertility Limited 的小股东。CARE Fertility 向患者提供经过验证的算法延时胚胎选择，作为辅助治疗选择，需额外付费。试用注册号 不适用。是CARE Fertility Limited 的小股东。CARE Fertility 向患者提供经过验证的算法延时胚胎选择，作为辅助治疗选择，需额外付费。试用注册号 不适用。