Endometrial Thickness May Not Impact Live Birth Rate Following Frozen Embryo Transfer

TUESDAY, Aug. 19, 2025 (HealthDay News) — For patients undergoing single euploid frozen embryo transfer, endometrial thickness (ET) may not significantly impact the live birth rate (LBR), according to a study published online July 10 in Human Reproduction.

Haley Genovese, M.D., from IVIRMA New Jersey in Basking Ridge, and colleagues conducted an international multicenter retrospective cohort study between January 2017 and December 2022 at 25 in vitro fertilization centers in three countries, including 30,676 cycles (78.6, 2.5, and 19.0 percent programmed, natural, and modified natural cycles [NCs and mNCs], respectively) to examine whether ET impacts LBR in patients undergoing single euploid frozen embryo transfer.

The researchers found that the median ET among all cycle types at all centers was 8.9 mm. In both programmed cycles and mNCs, conditional density plots showed a decline in LBR for ET <7 mm, with the odds of LBR reduced by 22 and 41 percent, respectively (adjusted odds ratios, 0.78 and 0.59, respectively). There was no ET threshold at which LBR was impacted in patients undergoing natural cycles. Sensitivity analyses were consistent with the overall analysis. Two models were developed to determine the prognostic value of ET in prediction of live birth; there was no significant difference in the performance of the model with versus without ET, indicating that ET is not a strong predictor of LBR.

“It”s likely not the thin lining itself that is causing the problem, but rather an underlying mechanism that is both driving a more persistent thin lining and causing less successful embryo implantation,” principal author Emre Seli, M.D., also from IVIRMA New Jersey, said in a statement.

One author disclosed ties to the biopharmaceutical industry.

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