The Extended Letrozole Regimen in Clomiphene Resistant Polycystic Ovary Syndrome and Its Effect on Endometrial Thickness and Uterine Artery Doppler Indices (Pulsatility and Resistive Indices)

Background & Objective: Polycystic Ovary Syndrome (PCOS) is the most common cause of anovulatory infertility. Ovulation‑inducing agents such as Clomiphene Citrate (CC) and Letrozole (LE) are widely used; however, approximately 15% of women with PCOS are resistant to CC. Successful conception requires adequate endometrial receptivity, which can be assessed using ultrasonography and Doppler studies. This study aimed to evaluate the effect of a fixed‑dose extended letrozole regimen on endometrial receptivity-assessed by endometrial thickness, endometrial volume, and uterine artery Doppler indices in CC‑resistant PCOS patients.Materials & Methods: This prospective interventional study was conducted at the High Institute for Infertility Diagnosis and Assisted Reproductive Technologies, Al Nahrain University, Baghdad, Iraq, between March 2023 and March 2024. A total of 54 infertile women aged 20-40 years with a confirmed diagnosis of PCOS and documented CC resistance were enrolled. Endometrial thickness, endometrial volume, and uterine artery Doppler indices (Pulsatility Index [PI] and Resistive Index [RI]) were assessed after CC treatment and following an extended letrozole regimen (5 mg daily for 10 days).Results: Letrozole treatment was associated with a significant increase in endometrial thickness, endometrial volume, PI, and RI compared with CC treatment (P<0.05 for all). Endometrial thickness showed a significant inverse correlation with patient age after letrozole therapy (r= -0.38, P=0.005).Conclusion: Extended‑duration letrozole therapy significantly improves endometrial receptivity parameters in women with CC‑resistant PCOS and represents an effective option for ovulation induction following CC failure.