title: Randomized, controlled pilot trial of natural versus hormone replacement therapy cycles in frozen embryo replacement in vitro fertilization.
abstract: OBJECTIVE
  To determine whether there is any difference between the outcomes of two standard treatment protocols for frozen embryo replacement (FER): natural and down-regulated hormone replacement treatment (HRT).
  
  
  METHODS
  Open, single-center, randomized, controlled pilot trial.
  
  
  METHODS
  Private fertility clinic.
  
  
  METHODS
  Women (n = 159) planning an FER cycle at the Oxford Fertility Unit, aged <40 years at the time their embryos were frozen; with at least one blastocyst or two cleavage-stage embryos in storage; regular ovulatory cycles; and at most two previous FER cycles.
  
  
  METHODS
  Eligible participants were recruited and randomized between March 2010 and July 2012 into one of two standard FER treatment groups: natural (n = 80) menstrual (Natural) or GnRH agonist/HRT (n = 79) cycles.
  
  
  METHODS
  Live birth rate after replacement of frozen-thawed embryos, clinical pregnancy rate, implantation rate, and cycle cancellations.
  
  
  RESULTS
  A total of 159 women were randomized (80 Natural; 79 HRT), and 145 had ET and completed the study (72 Natural; 73 HRT). Pregnancy outcomes were not significantly different between the two groups. The live birth rates were 26.3% (Natural) and 31.7% (HRT) per randomized patient. Per ET/protocol the live birth rates were 29.2% and 34.2%. The implantation rates were 24.3% and 26.0%, and there were three twin births in the Natural and five in the HRT arms.
  
  
  CONCLUSIONS
  The findings of this pilot study support the suggestion that for women with ovulatory cycles undergoing FER, the outcomes are similar between natural and HRT protocols.
  
  
  BACKGROUND
  NCT00843570. Registered at www.clinicaltrials.gov.
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, Institute of Reproductive Sciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Ginny
authors.initials: G
authors.lastname: Mounce
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, Institute of Reproductive Sciences, University of Oxford, Oxford, United Kingdom; Oxford Fertility Unit, Institute of Reproductive Sciences, Oxford, United Kingdom.
authors.forename: Enda
authors.initials: E
authors.lastname: McVeigh
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, Institute of Reproductive Sciences, University of Oxford, Oxford, United Kingdom; Oxford Fertility Unit, Institute of Reproductive Sciences, Oxford, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Turner
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, Institute of Reproductive Sciences, University of Oxford, Oxford, United Kingdom; Oxford Fertility Unit, Institute of Reproductive Sciences, Oxford, United Kingdom. Electronic address: tim.child@obs-gyn.ox.ac.uk.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Child
mesh_terms: D000328:Adult; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D005615:Freezing; D020249:Hormone Replacement Therapy / Q000379:methods*; D006801:Humans; D008597:Menstrual Cycle / Q000097:blood / Q000502:physiology; D018587:Oocyte Donation; D010865:Pilot Projects; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate
keywords: IVF; In vitro fertilization; frozen embryo replacement