Objective

2

To compare the clinical performance of three endometrial preparation protocols

including natural cycle (NC)

letrozole mild-stimulation cycle (LSC) and hormone replacement therapy (HRT)

in polycystic ovary syndrome (PCOS) patients undergoing frozen-thawed blastocyst transfer (FET)

and to identify their independent effects on live-birth outcomes

so as to provide clinical evidence for protocol selection in this population.

Methods

2

PCOS patients receiving FET at our centre were retrospectively enrolled and divided into NC

LSC and HRT groups according to endometrial preparation regimens. Baseline characteristics

ultrasound-derived endometrial receptivity markers

pregnancy and obstetric outcomes were compared among groups. Multivariate logistic regression was performed to adjust for confounders and analyse the independent impact of each protocol on live birth.

Results

2

No significant inter-group differences were found in key confounders such as duration of infertility

body mass index (BMI) and high-quality blastocyst proportion. The LSC group achieved favourable endometrial thickness and markedly reduced cycle cancellation caused by spontaneous ovulation failure observed in the NC group. After adjusting for all confounding variables

HRT was an independent adverse factor for live birth in PCOS patients

with an adjusted OR of 0.524

and the HRT group presented a higher early miscarriage rate. No statistically significant difference in live-birth outcomes was detected between the LSC and NC groups.

Conclusion

2

The letrozole mild-stimulation protocol restores near-physiological endocrine rhythms. It yields comparable live-birth efficiency to the natural cycle while lowering cycle-cancellation risk

and avoids the decreased live-birth rate and elevated early miscarriage risk associated with HRT. It is therefore the preferred endometrial preparation strategy for FET in PCOS patients.