['Ovarian stimulation is an essential part of assisted reproduction treatments. Research on whether the duration of stimulation alters the success in assisted reproduction has not been conclusive.', 'The purpose of the study was to establish whether the duration of ovarian stimulation alters the success in assisted reproduction treatments.', 'All fresh (non-donor) stimulation cycles performed in an academic tertiary referral ART centre over a period of 18\xa0years, between 1st January 1997 and 31st December 2014, were identified. Data were prospectively and electronically collected. IVF and ICSI cycles were analysed independently. Each category was then subdivided into assisted reproduction cycles where the antagonist, long (down regulation) and flare protocol were used. Clinical pregnancy was the main outcome measured. A total of 10,478 stimulation cycles (6011 fresh IVF and 4467 fresh ICSI) reaching egg collection were included.', 'We showed no significant difference in CP rates in IVF cycles for the long (p\xa0=\xa00.082), antagonist (p\xa0=\xa00.217) or flare (p\xa0=\xa00.741) protocol cycles or in ICSI cycles with the long (p\xa0=\xa00.223), antagonist (p\xa0=\xa00.766) or the flare (p\xa0=\xa00.690) protocol with regards the duration of stimulation.'] Does the duration of gonadotropin stimulation alter the clinical pregnancy rate in IVF or ICSI cycles?