Abstract
BackgroundSuccessful implantation and delivery require both the functional embryo and receptive endometrium in assisted reproductive technology (ART) cycles. However, little is known about embryo-endometrial interaction on live-birth. We aimed to investigate the independent effect and interaction of endometrial thickness (EMT) and embryo quality on live-birth in fresh embryo transfer (ET) cycles.MethodsWe conducted a retrospective cohort study including 15,012 ART cycles between 2013 and 2016 in three centers in China. Poisson regression with generalized estimating equations was employed to calculate relative risks (RRs) and 95% confidence intervals (CIs). We estimated the interaction of embryo quality and EMT on live-birth rate (LBR).ResultsThe LBR per cycle was 42.8% overall. LBR increased with increasing EMT and reached a plateau (50.6 to 54.2%) when EMT was 11 mm or thicker. Embryo quality represented by cumulative score was associated with LBR independently of number of embryos transferred and EMT. LBR was not increased with thicker EMT when only Q1 cleavage-stage embryo transferred (aRR 0.95, 95%CI 0.61–1.46). LBR was not increased significantly with thicker EMT with transfer of two good-quality cleavage-stage embryos and any blastocyst combination except Q1 group. There was significant interaction between EMT and embryo quality on LBR for cleavage-stage ETs (P=0.023).ConclusionsThis study demonstrated the nonlinear EMT-LBR association and the EMT cut-off value of 11 mm which may be of more clinical significance for predicting live-birth. Embryo quality is an independent prognostic tool for LBR. Our finding of significant embryo-endometrial interaction indicates combination of EMT and embryos quality might improve the prognostic value in clinical practice for live-birth in patients undergoing transfer of 1–2 fresh cleavage-stage embryos.
Highlights
Successful implantation and delivery require both the functional embryo and receptive endometrium in assisted reproductive technology (ART) cycles
live-birth rate (LBR) per cycle elevated from 39.5 to 46.2% with year of transfer. 94.8% of cycles transferred cleavage-stage embryos while only 5.2% transferred blastocysts. 71.7% of cycles had two embryos transferred while 28.3% had a single embryo transfer (ET), and after comparisons, LBR per cycle was significantly higher for two ETs than only one embryo (48.2% vs. 29.1%, P
Effect of endometrial thickness (EMT) on LBR of fresh in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles The LBR increased with increasing EMT on human chorionic gonadotropin (hCG) day as either a continuous variable or ordinal categories after adjusting the confounders
Summary
Successful implantation and delivery require both the functional embryo and receptive endometrium in assisted reproductive technology (ART) cycles. As an indicator of endometrial receptivity, endometrial thickness (EMT) on the day of human chorionic gonadotropin (hCG) administration has been reported and reaffirmed as a potential prognostic tool for ART outcomes in multiple studies [6,7,8], despite significant advancements of ultrasonic [9], immunologic [10] and molecular [11] markers for endometrial receptivity It remains a controversial issue, it has been widely suggested that a thin endometrium is associated with lower chance to conceive after IVF/ICSI, with cut-off values of EMT varying 7–9 mm in earlier studies [6, 12]. In a one-center study of 3350 IVF cycles, the non-linear association of EMT with live-birth was shown and required verification [7]
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