P-777 Can endometrial compaction predict live birth/ongoing pregnancy rates in assisted reproductive technology cycles? A systematic review and meta-analysis
Authors: Turkgeldi E , Kalafat E , Yildiz S , Keles I , Ata B , Bozdag G 
Published: June 2023

Abstract

Study question
Can endometrial compaction (EC) predict live birth/ongoing pregnancy rates (LBR/OPR) in assisted reproductive technology (ART) cycles?

Summary answer
Our meta-analysis shows that LBR/OPRs are similar in cycles with or without EC. Analysis of studies with euploid embryo transfers (ETs) also yield similar LBR/OPR.

What is known already
EC is a novel concept, defined as a change in endometrial thickness (EMT) between the end of follicular phase and ET day. Early studies implied that EC can be a predictor for improved LBR/OPRs in ART. However, subsequent studies presented conflicting results. The role of EC in predicting ART success remains undetermined and there is paucity of data whether a subgroup of women exists for whom EC may be predictive for ART success.

Study design, size, duration
We performed a systematic review and meta-analysis of studies reporting LBR/OP with regard to EC. Two independent authors searched electronic databases from the date of inception until January 29, 2023. Primary outcome was LBR/OPR per ET. Secondary outcomes were clinical pregnancy (CP) and miscarriage rates per ET. For dichotomous outcome measures, Mantel-Haenszel risk ratios (RRs); with 95% CIs are presented. A fixed or random effects model was used based on heterogeneity of the data.

Participants/materials, setting, methods
Initial search yielded 4816 studies. After exclusion through titles, 81 studies were assessed by reading their abstracts. Full text of 22 studies were evaluated. Finally, 16 studies involving a total of 13976 cycles were included in the meta-analysis. Included studies were further scrutinized based on the definitions for EC, fresh or frozen-thawed ET, endometrial preparation methods and utilization of preimplantation genetic diagnosis. Data for primary and secondary outcomes were extracted by two authors independently.

Main results and the role of chance
In our meta-analysis of studies using a cut-off value of 5% change in EMT to define EC, LBR/OPR was similar in cycles with and without EC [RR = 1.10, 95%CI = 0.97 to 1.24; 11 studies, 6157 cycles]. When no cut-off was implemented and the minimum EMT changes were taken into account for each study, LBR/OPR rates were comparable between cycles showing EC or not [RR = 1.04, 95%CI = 0.96 to 1.12; 16 studies, 13976 cycles]. In concordance, analysis of the six studies with 2710 cycles reporting only euploid embryo transfers yielded similar LBR/OPR for cycles with and without EC [RR = 1.01, 95%CI = 0.90 to 1.12]. LBR/OPR was comparable for cycles demonstrating EC or not when only cycles with artificial hormonal preparation for frozen-thawed ET were analyzed [RR = 1.09, 95%CI = 0.97 to 1.21; 11 studies, 5811 cycles]. Regarding the secondary outcome parameters, with a cut-off of 5% change in EMT, clinical pregnancy rates [RR = 0.98, 95%CI = 0.90 to 1.07; 8 studies, 5578 cycles] and miscarriage rates [RR = 0.91, 95%CI = 0.69 to 1.19; 8 studies, 3413 cycles] were similar between compaction and no-compaction cycles.

Limitations, reasons for caution
Around 3/4 of the studies are retrospective. While most studies define EC as ≥ 5% change in EMT, some used 0% or 10%. Moreover, some studies presented data as “compaction” and “no compaction” while others preferred “compaction”, “same” and “expansion”. We combined “no change” and “expansion” groups as the ‘’non-compaction’’ group.

Wider implications of the findings
Once a promising predictor for ART success, EC does not seem to be helpful in predicting LBR/OPR and calculating EC may be obsolete. Moreover, analysis on euploid ETs imply that embryo, not EC, determines the outcome. Further studies, preferably on euploid ETs, with a homogeneous definition of EC are needed.

Trial registration number
Not applicablez