Embryos of optimal development reach blastocyst stage 116 ± 2 h after insemination. Usable D7 blastocysts represent nearly 5% of embryos in IVF with acceptable pregnancy and live birth rates, however data are still limited. Therefore, this study aimed to analyze the ongoing pregnancy rate (OPR) of D7 blastocysts in single euploid frozen embryo transfer (FET) cycles. An observational study was performed including 1527 FET cycles with blastocysts biopsied on D5 (N = 855), D6 (N = 636) and D7 (N = 36). Blastocysts were classified as good (AA/AB/BA), fair (BB) or poor (AC/BC/CC/CA/CB) (Gardner scoring). FETs were performed in natural cycles (NC) or hormone replacement therapy (HRT) cycles. Patient’s age differed significantly between D5, D6 and D7 blastocysts FET cycles (33.2 ± 5.6, 34.4 ± 5.3 and 35.9 ± 5.2, P < 0.001). OPRs were higher when D5 euploid blastocysts were transferred compared with D6 and D7 (56.0% vs. 45.3% and 11.1%, P < 0.001). Poor quality blastocysts were predominant in D7 blastocyst FET cycles (good quality: 35.4%, 27.2%, 5.6%; fair quality: 52.1%, 38.5%, 11.1%; poor quality: 12.5%, 34.3%, 83.3%, P < 0.001 for D5, D6 and D7 blastocysts; respectively). OPR was significantly reduced by D7 blastocyst FETs (OR = 0.23 [0.08;0.62], P = 0.004), patient’s BMI (OR = 0.96 [0.94;0.98], P < 0.001), HRT cycles (OR = 0.70 [0.56;0.88], P = 0.002) and poor quality blastocysts (OR = 0.33 [0.24;0.45], P < 0.001). OPR is significantly reduced with D7 compared with D5/D6 euploid blastocysts in FET cycles. The older the patient, the more likely they are to have an FET cycle with blastocysts biopsied on D7, therefore culturing embryos until D7 can be a strategy to increase OPR outcomes in patients ≥38 years.

受精后 116 ± 2 小时，最佳发育的胚胎达到囊胚阶段。可用的 D7 囊胚占 IVF 胚胎的近 5%，具有可接受的妊娠率和活产率，但数据仍然有限。因此，本研究旨在分析单个整倍体冷冻胚胎移植（FET）周期中D7囊胚的持续妊娠率（OPR）。进行了一项观察性研究，包括 1527 个 FET 周期，并在 D5 ( N = 855)、D6 ( N = 636) 和 D7 ( N = 36) 上进行囊胚活检。囊胚被分为良好（AA/AB/BA）、一般（BB）或差（AC/BC/CC/CA/CB）（加德纳评分）。FET 在自然周期 (NC) 或激素替代疗法 (HRT) 周期中进行。D5、D6 和 D7 囊胚 FET 周期之间患者的年龄存在显着差异（33.2 ± 5.6、34.4 ± 5.3 和 35.9 ± 5.2，P < 0.001）。与 D6 和 D7 相比，D5 整倍体囊胚移植时的 OPR 更高（56.0% vs. 45.3% 和 11.1%，P < 0.001）。D7 囊胚 FET 周期中质量差的囊胚占主导地位（质量良好：35.4%、27.2%、5.6%；质量一般：52.1%、38.5%、11.1%；质量差：12.5%、34.3%、83.3%，P < 0.001分别为 D5、D6 和 D7 囊胚）。D7 囊胚 FET (OR = 0.23 [0.08;0.62], P = 0.004)、患者 BMI (OR = 0.96 [0.94;0.98], P < 0.001)、HRT 周期 (OR = 0.70 [0.56;0.88)显着降低 OPR ]，P = 0.002）和质量差的囊胚（OR = 0.33 [0.24;0.45]，P < 0.001）。在 FET 周期中，与 D5/D6 整倍体囊胚相比，D7 的 OPR 显着降低。患者年龄越大，越有可能在第 7 天进行 FET 周期并进行囊胚活检，因此培养胚胎直至第 7 天可能是提高 ≥ 38 岁患者 OPR 结局的策略。