title: The effect of delayed initiation of gonadotropin-releasing hormone antagonist in a flexible protocol on in vitro fertilization outcome.
abstract: OBJECTIVE
  To determine the proportion of patients stimulated on a flexible GnRH antagonist regimen who meet the criteria for antagonist administration after stimulation day 6 (S6) and to compare their clinical characteristics and cycle outcome with those patients who start the antagonist on S6 or earlier.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Tertiary university hospital.
  
  
  METHODS
  Patients undergoing IVF (n = 442) using a flexible GnRH antagonist protocol.
  
  
  METHODS
  Ovarian stimulation was performed using gonadotropins and GnRH antagonists. Group A (n = 323) patients met the criteria for antagonist administration (follicle size >12 mm, E2 >300 pg/mL) on S6 or earlier. Group B patients (n = 119) started the antagonist later.
  
  
  METHODS
  Implantation rate.
  
  
  RESULTS
  Comparable implantation (30.4% vs. 33.7%), clinical (47.4% vs. 52.9%), and ongoing pregnancy rates (41.2% vs. 47.9%) were observed in groups A and B, respectively. Group B patients had a significantly higher body mass index, longer stimulation, increased gonadotropins dosage, fewer oocytes and two pronuclei oocytes, fewer frozen embryos, and fewer cycles with embryo freezing. Patients with polycystic ovary syndrome were more likely to be in group B.
  
  
  CONCLUSIONS
  A considerable proportion of patients on a flexible regimen begin GnRH antagonist administration later than S6. Despite different stimulation and laboratory characteristics, their reproductive outcome is not compromised as compared with patients with an earlier antagonist start.
authors.affiliation: IVF Unit, Department of Obstetrics and Gynecology, Edith Wolfson Medical Center, Holon, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Samer
authors.initials: S
authors.lastname: Tannus
authors.forename: Ariel
authors.initials: A
authors.lastname: Weissman
authors.forename: Mona
authors.initials: M
authors.lastname: Boaz
authors.forename: Eran
authors.initials: E
authors.lastname: Horowitz
authors.forename: Amir
authors.initials: A
authors.lastname: Ravhon
authors.forename: Abraham
authors.initials: A
authors.lastname: Golan
authors.forename: David
authors.initials: D
authors.lastname: Levran
mesh_terms: D000328:Adult; D015925:Cryopreservation; D010064:Embryo Implantation / Q000187:drug effects; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D007987:Gonadotropin-Releasing Hormone / Q000037:antagonists & inhibitors*; D006062:Gonadotropins / Q000008:administration & dosage; D006801:Humans; D007247:Infertility, Female / Q000188:drug therapy*; D009865:Oocytes / Q000187:drug effects; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D006062:Gonadotropins; D007987:Gonadotropin-Releasing Hormone