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.
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