Poulsen V, Ingerslev H J, Kirkegaard K
Department of Clinical Medicine, Aarhus University Hospital, Palle Juul Jensen Boulevard, 8200 Aarhus N, Denmark.
Fertility Clinic, Aalborg University Hospital, 9000 Aalborg, Denmark.
Hum Reprod. 2017 Jun 1;32(6):1238-1243. doi: 10.1093/humrep/dex059.
Is there a difference in pregnancy rates between embryos transferred electively on Day 5 and Day 6, respectively?
The chance of pregnancy is significantly reduced (odds ratio (OR): 0.34; 95% CI 0.22-0.52) if transfer is performed on Day 6 compared with Day 5.
Several studies report that Day 5 transfers have higher implantation rates (IRs) when compared with Day 6 transfers. These studies were based on non-elective Day 6 transfers, where transfers on Day 6 were performed with developmentally delayed embryos. Traditionally, difference in IRs has therefore been explained by an impaired embryo quality. An alternative explanation is that endometrial receptivity is higher on Day 5 compared with Day 6.
STUDY DESIGN, SIZE, DURATION: The study was conducted as a retrospective cohort follow-up study on single blastocyst transfers from February 2011 until August 2015 in patients aged <38 years, with ≥eight oocytes retrieved and no diagnosis of endometriosis. Non-elective Day 6 transfers were excluded. Post hoc power-calculations (two-sided level of significance 0.05, power of 0.80) indicate that 91 embryos were needed in each group to detect a reduction in IR (primary outcome) from 40 to 20%.
PARTICIPANTS/MATERIALS, SETTING, METHODS: Day 5 or Day 6 transfers were implemented accordingly: from 2011 till 2013, transfers were performed on Day 6. If Day 6 was a Sunday, patients received Day 5 transfers. From 2013 onward, blastocysts were transferred on Day 5. If Day 5 was a Sunday, the transfer was delayed to Day 6. Univariable logistic regression analysis was performed to identify potential confounders. Factors with a P-value <0.1 were included in the multivariable logistic regression analysis.
We included 334 single elective Day 5 and 268 elective Day 6 transfers. The unadjusted odds for implantation between Day 5 and Day 6 groups were 0.35 (95% CI 0.25-0.49). A univariable logistic regression analysis identified maternal age, BMI, cumulative FSH dose, number of cryopreserved embryos, score of inner cell mass and trophectoderm and day of transfer as predictors of clinical pregnancy. When adjusting for these variables in a multivariable logistic regression analysis, the implantation odds for Day 5 transfer remained significantly higher than Day 6 (OR 0.34; 95% CI 0.22-0.52).
LIMITATIONS, REASONS FOR CAUTION: The study was conducted on good prognosis patients. The majority of Day 6 transfers were performed in the beginning of the study period. Day 5 transfers were generally performed in the end of the study period. This difference in time of recruitment may cause a minor variation in the data but a subanalysis indicates that this potential variation is negligible. Day 5 scores were higher in the Day 5 transfer group.
Based on the findings in this study, transfers should be performed on Day 5. If Day 5 transfers are logistically impossible to perform, it is be preferable to cryopreserve the blastocyst and transfer in another cycle on Day 5, as Day 6 transfers should be avoided.
STUDY FUNDING/COMPETING INTEREST(S): None.
分别在第5天和第6天选择性移植胚胎，妊娠率是否存在差异？
与第5天移植相比，在第6天进行移植时，妊娠几率显著降低（优势比（OR）：0.34；95%置信区间0.22 - 0.52）。
多项研究报告称，与第6天移植相比，第5天移植具有更高的着床率（IRs）。这些研究基于非选择性的第6天移植，即第6天的移植是针对发育延迟的胚胎进行的。因此，传统上IRs的差异被解释为胚胎质量受损。另一种解释是，与第6天相比，第5天的子宫内膜容受性更高。
研究设计、规模、持续时间：该研究是一项回顾性队列随访研究，对2011年2月至2015年8月年龄<38岁、获卵数≥8个且未诊断为子宫内膜异位症的患者进行单囊胚移植。排除非选择性的第6天移植。事后功效计算（双侧显著性水平0.05，功效0.80）表明，每组需要91个胚胎才能检测到IR（主要结局）从40%降至20%。
参与者/材料、设置、方法：相应地实施第5天或第6天移植：2011年至2013年，在第6天进行移植。如果第6天是周日，则患者接受第5天移植。从2013年起，囊胚在第5天移植。如果第5天是周日，则移植推迟到第6天。进行单变量逻辑回归分析以识别潜在混杂因素。P值<0.1的因素纳入多变量逻辑回归分析。
我们纳入了334例第5天的单选择性移植和268例第6天的选择性移植。第5天和第6天组之间未调整的着床优势比为0.35（95%置信区间0.25 - 0.49）。单变量逻辑回归分析确定产妇年龄、BMI、累积促卵泡激素剂量、冷冻保存胚胎数、内细胞团和滋养外胚层评分以及移植日为临床妊娠的预测因素。在多变量逻辑回归分析中对这些变量进行调整后，第5天移植的着床优势比仍显著高于第6天（OR 0.34；95%置信区间0.22 - 0.52）。
局限性、谨慎原因：该研究是在预后良好的患者中进行的。大多数第6天移植是在研究期开始时进行的。第5天移植一般在研究期结束时进行。这种招募时间的差异可能会导致数据出现轻微变化，但亚分析表明这种潜在变化可忽略不计。第5天移植组的第5天评分更高。
基于本研究结果，应在第5天进行移植。如果在后勤方面无法在第5天进行移植，最好将囊胚冷冻保存，并在另一个周期的第5天进行移植，因为应避免在第6天移植。
研究资金/利益冲突：无。
