STUDY QUESTION Does the embryo cleavage pattern and rate of blastocyst formation differ between normal weight and obese women undergoing IVF? SUMMARY ANSWER Embryo morphokinetic development, final blastocyst formation rate and blastocyst morphology do not differ between obese and normal weight women. WHAT IS KNOWN ALREADY Female obesity has been related to impaired IVF outcomes. Although the mechanisms responsible for this detrimental effect are thought to include impaired oocyte and embryo quality and reduced endometrial receptivity, they are yet to be confirmed. Embryo quality has been commonly assessed using static morphological criteria. Only three studies have analysed the progress of embryos up to the blastocyst stage in women with elevated BMI, but they have used small samples of patients or have obtained contradictory results. STUDY DESIGN, SIZE, DURATION This retrospective, cohort study, was performed from January 2016 to May 2020. A total of 3316 ICSI cycles from 2822 women were included, of which 1251 cycles were part of a preimplantation genetic testing programme. In total, 17 848 embryos were analysed. PARTICIPANTS/MATERIALS, SETTING, METHODS This study reports on the IVF cycles of infertile women, with a known BMI, who underwent ICSI and whose embryos were grown until the fifth/sixth day of development in a time-lapse system. Patients were grouped as follows. Underweight was defined as a BMI <18.5 kg/m2; normal weight was a BMI of 18.5–24.9 kg/m2; overweight was a BMI of 25–29.9 kg/m2; and obesity was a BMI of ≥30 kg/m2. Embryo development was assessed on an external computer with analysis software. MAIN RESULTS AND THE ROLE OF CHANCE Despite an initial slower pattern of embryo development, the blastocyst formation rate on day 5 or on day 5 plus day 6 did not differ in obese women with respect to the other three BMI groups. Moreover, based on the evaluation of inner cell mass and the trophectoderm on both days of blastocyst development, embryo quality was similar across the BMI groups, as were the pattern of development and arrest up to blastocyst formation and the distribution of the categories of full, expanded and hatching blastocysts. LIMITATIONS, REASONS FOR CAUTION Limitations include the retrospective analysis of data, the use of BMI as the only parameter to define normal/abnormal female body weight, and the lack of complete information about clinical outcomes. WIDER IMPLICATIONS OF THE FINDINGS Blastocyst formation and embryo morphokinetics are not affected by female obesity, and the poorer IVF outcomes described for such women are probably due to deficient endometrial receptivity. The role of endometrial progesterone exposure on the day of embryo transfer should be analysed in future studies as a possible determining factor. STUDY FUNDING/COMPETING INTEREST(S) No external funding was used and there are no competing interests. TRIAL REGISTRATION NUMBER N/A.

中文翻译：

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肥胖和正常体重女性的囊胚形成相似：形态动力学研究

研究问题 正常体重和接受体外受精的肥胖女性的胚胎卵裂模式和囊胚形成率是否不同？总结 答案 胚胎形态动力学发育、最终囊胚形成率和囊胚形态在肥胖和正常体重女性之间没有差异。已知情况 女性肥胖与 IVF 结果受损有关。尽管造成这种有害影响的机制被认为包括卵母细胞和胚胎质量受损以及子宫内膜容受性降低，但它们尚未得到证实。胚胎质量通常使用静态形态学标准进行评估。只有三项研究分析了 BMI 升高的女性胚胎直至囊胚期的进展，但他们使用的患者样本很少或获得了相互矛盾的结果。学习规划，规模、持续时间 这项回顾性队列研究于 2016 年 1 月至 2020 年 5 月进行。共纳入来自 2822 名女性的 3316 个 ICSI 周期，其中 1251 个周期是植入前基因检测计划的一部分。总共分析了 17,848 个胚胎。参与者/材料、设置、方法 本研究报告了不孕妇女的体外受精周期，这些妇女的体重指数已知，她们接受了 ICSI，其胚胎在延时系统中生长到发育的第五/第六天。患者分组如下。体重过轻定义为 BMI <18.5 kg/m2；正常体重是 18.5–24.9 kg/m2 的 BMI；超重是 25–29.9 kg/m2 的 BMI；肥胖是 BMI ≥ 30 kg/m2。在带有分析软件的外部计算机上评估胚胎发育。主要结果和机会的作用 尽管最初的胚胎发育模式较慢，但肥胖女性在第 5 天或第 5 天加第 6 天的囊胚形成率与其他三个 BMI 组相比没有差异。此外，根据对囊胚发育两天内细胞团和滋养外胚层的评估，BMI 组的胚胎质量相似，发育和停滞直至囊胚形成的模式以及完整、膨胀和孵化的囊胚。局限性、谨慎的原因 局限性包括数据的回顾性分析、使用 BMI 作为定义正常/异常女性体重的唯一参数，以及缺乏有关临床结果的完整信息。研究结果的更广泛意义 胚泡形成和胚胎形态动力学不受女性肥胖的影响，这些女性的 IVF 结果较差可能是由于子宫内膜容受性不足。在未来的研究中，应将子宫内膜黄体酮暴露在胚胎移植当天的作用作为可能的决定因素进行分析。研究资金/竞争利益 没有使用外部资金，也没有竞争利益。试用注册号 不适用。研究资金/竞争利益 没有使用外部资金，也没有竞争利益。试用注册号 不适用。研究资金/竞争利益 没有使用外部资金，也没有竞争利益。试用注册号 不适用。