Results: The rates of clinical and ongoing pregnancies per stimulated cycle were significantly (P < 0.01 and P < 0.05, respectively) higher in surge group (41% and 34% in 71 cycles) than control (18% and 15% in 71 cycles). In surge group 86% and 14% of 14 hormone-measured women showed increase and plateau, respectively, in serum LH levels after administration of buserelin and hCG, while all of 11 hormone-measured women in control group showed decrease in LH after hCG (incidence of LH surge: 86%

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... vs. 0%, P < 0.0001). The profiles of GH and P4 changes around hCG administration also significantly differed between surge and control groups. Conclusions: Under pituitary desensitization by nasal administration of GnRH agonist, diminishied but significant LH surge can be induced by administration of GnRH agonist at increased dosage within one hour before hCG. This novel protocol significantly improved embryonic development and ongoing pregnancy rate, suggesting critical role of mid-cycle surge of LH and other hormones in oocyte maturation. O-116 Comparison between start of ovarian stimulation on cycle day 2 versus cycle day 5 with GnRH antagonist in IVF treatment: a randomized controlled trial