Hemoglobin A1c (Hba1c) as a Novel Biomarker of Embryo Competence and Pregnancy Success in Non-Diabetic Single Frozen Embryo Transfer (Sfet) Cycles

Objective: To evaluate whether pre-retrieval HbA1c predicts embryo competence and clinical pregnancy rate (CPR) in non-diabetic patients undergoing single frozen embryo transfer (sFET). Design: Retrospective cohort study Materials and Methods: 321 sFET cycles from non-diabetic women (HbA1c <6.5%) from January 2024 to December 2025 were included. Linear regression assessed HbA1c as a predictor of blastocyst count (BC), blastocyst-to-fertilized oocyte ratio (BFOR), and top- quality embryo (TQE) count defined as Gardner grade ≥2BB. Models were adjusted for age, body mass index (BMI), anti-mullerian hormone, ovulatory polycystic ovarian syndrome status and total gonadotropin dose. Logistic regression assessed CPR, adjusted for HbA1c, BMI and age. Significance was set at p<0.05. Results: Mean age was 35.4±4.1 years and mean BMI was 26.5±6.0. Mean HbA1c was 5.36±0.28% (range 4.2–6.3%), drawn a median of 4.0 months before retrieval. Among 280 complete cycles, each 0.7% rise in HbA1c was significantly associated with 1 fewer blastocyst (p=0.014). After adjustment for oocytes retrieved, this association was attenuated but directionally consistent (β = −0.931 per 1% HbA1c). HbA1c was associated with BFOR after adjustment for retrieved oocytes (p = 0.045), equivalent to 1 fewer blastocyst per 15 fertilized oocytes. Among 177 cycles with TQE data, each 0.5% rise in HbA1c was associated with 1 fewer TQE (β=−2.075, p<0.001; ΔR²=0.049). In 147 transfer cycles, CPR was 79.6% (117/147). Higher HbA1c was associated with lower pregnancy odds in exploratory analysis adjusted for age and BMI (OR=0.157 per 1% HbA1c, p=0.032). Conclusions: Subtle HbA1c elevations below the diabetic threshold were associated with fewer blastocysts, fewer TQE, lower embryo conversion efficiency and lower CPR. HbA1c may represent a readily available IVF biomarker warranting prospective study in non-diabetic patients.