ObjectiveTo compare the clinical outcomes of different pituitary down regulation protocols with gonadotropin-releasing hormone agonist (GnRH-a) in patients undergoing in vitro fertilization and embryo transfer (IVF-ET) treatment. MethodsThe clinical data of 358 IVF cycles in women at 40 years old or younger from November 2012 to January 2013 in the West China Second University Hospital were analyzed retrospectively. All the 358 cycles were divided into two groups, according to whether the leading follicle diameter was <14 mm (group A, 158 cycles) or ≥14 mm (group B, 200 cycles) after discontinuing the GnRH-a. The clinical outcomes were compared between the two groups. ResultsCompared with group B, the amount of gonadotropins used was significantly more, and the time of gonadotropin use was also significantly longer in group A (P<0.05). However, the serum level of estradiol (E2), progesterone (P) and Luteinizing hormone (LH), incidence of premature P rise, retrieved ovum number, the rates of implantation, clinical pregnancy, miscarriage and live birth did not significantly differ between the two groups (P>0.05). ConclusionDiscontinuing the use of GnRH-a in early stage of controlled ovarian stimulation can keep effective pituitary down regulation and it has the same optimal clinical outcomes in patients undergoing IVF-ET.