Pregnancy Outcomes for Day 5 Versus Day 6 Single Frozen-thawed Blastocyst Transfer with Different Qualities of Embryos: A Large Matched-cohort Study

Objective This study aimed to determine whether the day of blastocyst expansion affects pregnancy outcomes in frozen-thawed blastocyst transfer(FBT)cycles.Methods A retrospective match-cohort study was conducted.Patients who underwent blastocyst transfer in frozen-thawed cycles at day 5 or 6 were matched for potential confounding factors.A total of 2207 matched pairs of FBT cycles were included from January 2016 to December 2019 in our Reproductive Medicine Center.Results The clinical pregnancy rate(CPR)and live birth rate(LBR)were significantly increased in day 5 blastocyst transfers when compared to day 6 blastocyst transfers,in terms of the same embryo quality.For FBT cycles with good-quality embryo,the CPR at day 5 and 6 was 61.30%and 57.56%,respectively(P=0.045),and the LBR was 44.79%and 36.16%,respectively(P<0.001).For FBT cycles with poor-quality embryo,the CPR at day 5 and 6 was 48.61%and 40.89%,respectively(P=0.006),and the LBR was 31.71%and 25.74%,respectively(P=0.019).The CPR for FBT cycles with good-quality embryo was statistically higher at day 6 than that at day 5 with poor-quality embryo transferred(57.56%vs.48.61%,P=0.001).Maternal age,anti-Müllerian hormone(AMH),endometrial thickness,embryo quality,and the day of blastocyst expansion were independently correlated with the CPR and LBR.The FBT cycles at day 5 had significantly higher CPR(adjusted odds ratio[OR]=1.246,95%confidence intervals[CI]:1.097–1.415,P=0.001)and LBR(adjusted OR=1.435,95%CI:1.258–1.637,P<0.001)than those at day 6.Conclusion The embryo quality is the primary indicator for FBT cycles.Day 5 blastocysts should be preferred when the quality of embryo at day 5 is the same as that at day 6.

Pregnancy Rate after Embryo Transfer on Day 5 and Day 6 in IVF. A Systematic Review and Meta-Analysis

Study Question: The question: is there any difference in pregnancy rate between embryo transfer day 5 and day 6 in IVF? What Is Known Already? Blastocyst transfer is increasingly popular in assisted reproductive technology (ART) centers today. Very few articles concentrate on comparing Day 5 and Day 6 embryo transfer with conflict results. Objective, Study Design: Systematic review and meta-analysis of published controlled studies. Searches conducted from 2001-2020 on PubMed. Medline, EMBASE, and ISI Web of Science Electronic database is used to collect data, using the following search terms: blastocyst, Day 5, Day 6, embryo transfer (E.T.) and pregnancy rate. Materials, Setting, Methods: A total of 6 full-text articles preselected from 211 references, based on title and abstract. Two independent reviewers performed data selection and extraction according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement (PRISMA). This systematic review was conducted according to (PICO) standard. Random-effect meta-analysis performed on all data (overall analysis). Results and the Role of Chance: Data from 6 relevant articles were extracted and integrated into the meta-analysis that reported clinical pregnancy rate (CPR) as an outcome in 5640 cycles, 2274 cycle had embryo transfer at day 6 and the control was 3366 cycle had embryo transfer day 5 showed a significantly higher clinical pregnancy rate following Day 5 embryo transfer compared with Day 6 embryo transfer with odd ratio and 95% confidence limit 0.73 (0.66 - 0.82) p value < 0.000. Sensitivity analysis led to similar results and conclusions. Limitations, Reasons for Caution: The validity of meta-analysis results depends mainly on the quality and the number of published studies available. Indeed, this meta-analysis included no randomized controlled trial (RCT). Wider Implications of the Findings: In regards to the results of this original meta-analysis, ART practitioners should preferably transfer D5 rather than D6 blastocysts. Further RCTs are needed to address the question of whether D6 embryos should be transported.

青藏高原草地物候动态及其对驱动因子的响应

植被物候动态是多重因子影响的结果,尤其在对外界扰动响应敏感的青藏高原草地生态系统。本研究利用2000-2020年MODIS 16 d合成的归一化植被指数(normalization difference vegetation index, NDVI)数据,选用动态阈值法提取了青藏高原逐年的植被物候期,探究了青藏高原草地物候动态变化及其对驱动因子的响应。结果表明:1) 2000-2020年青藏高原草地生长季始期(start of the growing season, SOS)从西北向东南呈提前趋势,每年提前约0.19 d;草地生长季末期(end of the growing season, EOS)整体呈推迟趋势,每年推迟约0.19 d;草地生长季长度(length of the growing season, LOS)由西北向东南逐渐增长。2)风速和连续5 d最大降雨(yearly maximum five-day precipitation, RX5day)是影响草地LOS的主要因素,且因子间两两交互作用要强于单个因子对植被物候的影响,尤其表现在RX5day与温度和风速与温度之间的交互。3)草地LOS与风速和RX5day的回归系数有明显的空间异质性。藏北高原草地LOS随风速增大而变长,随RX5day增大而变短。青海高原和藏南谷地的草地LOS随风速增大而变短。川藏高山峡谷区草地LOS随RX5day增大而变长。综上,本研究可为研究区内生态系统保护和畜牧业的发展提供一定科学依据。