OBJECTIVE: Study effect of stimulation protocol on LUF risk & luteal phase profile in PCOS with LUF.DESIGN: Prospective observational studyMATERIALS AND METHODS: 964 cycles in 696 PCOS infertile women (cycle number range 1-3 cycles/patent) monitored by TVS and serum midluteal progesterone (MLP4) under different induction protocols: CC only (426 cycles), sequential CC-and hMG (462 cycles), and hMG only (76 cycles).Cases were started on CC .If CC resistance, anovulation or LUF occurs, sequential CC-hMG or hMG only are given next cycle. TVS monitoring was started on day -5, every other day till day + 7, the day of HCG is day 0. Ovulation was triggered by 10000 IU HCG when leading follicle reached ≥18 mm mean diameter. MLP4 was measured on day +7 Outcome measurements were ovulation (TVS evidence of follicular rupture and MLP4 ≥ 1.5 ng/mL), anovulation (failure of follicular rupture and MLP4 < 1.5 ng/mL), LUF (failure of follicular rupture with MLP4 ≥1.5 ng/mL) and pregnancy. Comparisons between group means for continuous normally distributed variables was made by t-test, and between categorical variables was made by χ tests from which the relative risk (RR 95% CI) was derived .Non parametric correlation test was done to measure correlation of nonparametric variablesRESULTS: In CC cycles, LUF incidence was 15.1% compared to 6.9% in sequential CC-hMG (RR 2.2, 95%CI 1.4- 3.2), 5.2% in hMG (RR 2.8, 95% CI 1.1-7.4).We found significant correlation between LUF incidence and use of CC protocol. Consecutive cycle stimulation is not associated with increased LUF incidence. Only 7.1 % of LUF recurred in consecutive cycles. Compared to normal ovulatory cycles LUF had significantly lower MLP4, shorter luteal phase length, and zero pregnancy rateCONCLUSIONS: Risk of LUF in PCOS is significantly increased in cycles stimulated by CC compared with sequential CC-hMG & hMG protocols and is more related to stimulation protocol than to patient type or cycle repetition. LUF cycles show more luteal phase defect and are non-conception cycles OBJECTIVE: Study effect of stimulation protocol on LUF risk & luteal phase profile in PCOS with LUF. DESIGN: Prospective observational study MATERIALS AND METHODS: 964 cycles in 696 PCOS infertile women (cycle number range 1-3 cycles/patent) monitored by TVS and serum midluteal progesterone (MLP4) under different induction protocols: CC only (426 cycles), sequential CC-and hMG (462 cycles), and hMG only (76 cycles).Cases were started on CC .If CC resistance, anovulation or LUF occurs, sequential CC-hMG or hMG only are given next cycle. TVS monitoring was started on day -5, every other day till day + 7, the day of HCG is day 0. Ovulation was triggered by 10000 IU HCG when leading follicle reached ≥18 mm mean diameter. MLP4 was measured on day +7 Outcome measurements were ovulation (TVS evidence of follicular rupture and MLP4 ≥ 1.5 ng/mL), anovulation (failure of follicular rupture and MLP4 < 1.5 ng/mL), LUF (failure of follicular rupture with MLP4 ≥1.5 ng/mL) and pregnancy. Comparisons between group means for continuous normally distributed variables was made by t-test, and between categorical variables was made by χ tests from which the relative risk (RR 95% CI) was derived .Non parametric correlation test was done to measure correlation of nonparametric variables RESULTS: In CC cycles, LUF incidence was 15.1% compared to 6.9% in sequential CC-hMG (RR 2.2, 95%CI 1.4- 3.2), 5.2% in hMG (RR 2.8, 95% CI 1.1-7.4).We found significant correlation between LUF incidence and use of CC protocol. Consecutive cycle stimulation is not associated with increased LUF incidence. Only 7.1 % of LUF recurred in consecutive cycles. Compared to normal ovulatory cycles LUF had significantly lower MLP4, shorter luteal phase length, and zero pregnancy rate CONCLUSIONS: Risk of LUF in PCOS is significantly increased in cycles stimulated by CC compared with sequential CC-hMG & hMG protocols and is more related to stimulation protocol than to patient type or cycle repetition. LUF cycles show more luteal phase defect and are non-conception cycles