Comparative Effects of Letrozole 7.5 mg versus 5.0 mg on Follicular Growth in Sub-fertile Women with Polycystic Ovary Syndrome

Open Access

Abstract

Background: PCOS is a common cause of anovulatory subfertility in reproductive-aged women. Letrozole is a first-line ovulation induction agent, but the optimal starting dose is unclear. The study aims to compare letrozole 7.5 mg versus 5.0 mg for follicular growth in subfertile women with PCOS. Methods and materials: This quasi-experimental study (June 2023 to January 2025) was conducted in the Department of Obstetrics and Gynecology, BIRDEM General Hospital. Eighty subfertile women aged 18–35 years with Rotterdam-diagnosed PCOS, on metformin, were enrolled and allocated into two groups: letrozole 5 mg/day or 7.5 mg/day from cycle day 2–6. Follicular growth was measured by transvaginal ultrasound on day 2 and day 12, response was categorized by follicle size, and adverse effects were recorded. Results: Baseline characteristics were comparable between groups, with no significant differences in age, BMI, subfertility type, or subfertility duration. On Day 12, letrozole 7.5 mg produced a significantly larger leading follicle than 5 mg (16.81 ± 5.06 vs 13.28 ± 6.92 mm; p<0.001), with higher optimal response (67.5% vs 42.5%) and more dominant follicles (67.5% vs 42.5%; p=0.025), and fewer non-responders (12.5% vs 35.0%). Follicular size increased significantly from Day 2 to Day 12 in both arms (p<0.001 for 5 mg, p=0.003 for 7.5 mg). Adverse effects were infrequent and similar across doses, and most participants reported no side effects (90.0% vs 85.0%; p=0.74). Conclusion: Letrozole 7.5 mg achieved better Day 12 follicular growth and more dominant follicles than 5 mg, with similar adverse effects, supporting 7.5 mg as a more effective starting dose under ultrasound monitoring in PCOS subfertility.