In an attempt to examine the influence of BMI on IVF outcome in patients undergoing COH with either GnRH-agonist or antagonist, the investigators found that while in patients with BMI>25 kg/m2, COH with either GnRH-agonist or antagonist achieved a comparable outcome, in those with BMI<25 kg/m2, the use of GnRH-agonist suppressive protocol revealed a significantly higher pregnancy rates.