Endometrial Thickness and Ectopic Pregnancy Risk following in vitro Fertilization Embryo Transfer: A Systematic Review and Meta-Analysis.

Abstract

Background: Endometrial thickness is a significant determinant of pregnancy outcomes following in vitro fertilization embryo transfer (IVF-ET). However, the relationship between endometrial thickness and the risk of ectopic pregnancy after IVF-ET remains debated.

Methods: We conducted a comprehensive literature search of the PubMed, Cochrane Library, and Embase databases to identify relevant studies. In fresh embryo transfer cycles, endometrial thickness was measured on the day of hCG triggering; in frozen-thawed embryo transfer cycles, measurement was performed during the endometrial preparation phase prior to embryo transfer. The ectopic pregnancy rate was designated as the primary outcome measure. Pairwise meta-analyses were performed using Review Manager 5.3.

Results: A total of ten studies met the inclusion criteria. In the meta-analysis, women with a thin endometrium undergoing IVF-ET had a significantly higher risk of ectopic pregnancy compared with those with a non-thin endometrium (odds ratio [OR] 2.27, 95% confidence interval [CI] 1.78-2.91, I2 = 48%). Subgroup analyses showed consistent findings in both fresh embryo transfer (OR 2.58, 95% CI 1.62-4.10, I2 = 23%) and frozen-thawed embryo transfer cycles (OR 2.16, 95% CI 1.61-2.89, I2 = 60%). When thin endometrium was defined as <7 mm or <8 mm, the risks remained elevated (OR 2.00 and 2.36, respectively).

Conclusion: In IVF-ET cycles, a thin endometrium is associated with a significantly increased ectopic pregnancy rate. No optimal thickness range can be identified from the available data due to the lack of individual patient information and the absence of dose-response analyses.