title: Comparison of birth weights in patients randomly assigned to fresh or frozen-thawed embryo transfer.
abstract: OBJECTIVE
  To estimate birth weight differences between patients randomized to fresh or thawed ET.
  
  
  METHODS
  Post hoc analysis of results from two similar randomized trials.
  
  
  METHODS
  Private fertility center.
  
  
  METHODS
  One hundred thirty-four first-time IVF patients, ages 18-40 years at oocyte retrieval, who had live birth.
  
  
  METHODS
  Patients were randomly assigned to have either fresh blastocyst transfer or all bipronuclear oocytes frozen followed by thaw, extended culture, and blastocyst transfer in a subsequent cycle. Preimplantation genetic screening was not allowed.
  
  
  METHODS
  Mean birth weight.
  
  
  RESULTS
  After allowing for the contributions of multiple significant variables (gestational age at birth, the presence of a vanished twin, number of infants delivered) in multiple linear regression, the adjusted mean birth weight was 166 g (95% confidence interval, 43-290 g) lower after fresh blastocyst transfer when compared with transfer of blastocysts derived from thawed bipronuclear oocytes.
  
  
  CONCLUSIONS
  Birth weights are lower in cycles with fresh blastocyst transfer after controlled ovarian stimulation than in transfers of frozen-thawed embryos in the absence of ovarian stimulation. This finding confirms similar results reported in many retrospective studies.
  
  
  BACKGROUND
  NCT00963625 and NCT00963079.
authors.affiliation: Fertility Center of Las Vegas and University of Nevada School of Medicine, Las Vegas, Nevada. Electronic address: bsshapiro@aol.com.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Shapiro
authors.affiliation: Fertility Center of Las Vegas and University of Nevada School of Medicine, Las Vegas, Nevada.
authors.forename: Said T
authors.initials: ST
authors.lastname: Daneshmand
authors.affiliation: Fertility Center of Las Vegas and University of Nevada School of Medicine, Las Vegas, Nevada.
authors.forename: Carrie E
authors.initials: CE
authors.lastname: Bedient
authors.affiliation: Fertility Center of Las Vegas and University of Nevada School of Medicine, Las Vegas, Nevada.
authors.forename: Forest C
authors.initials: FC
authors.lastname: Garner
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D004624:Embryo Transfer / Q000009:adverse effects; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro / Q000009:adverse effects; D006801:Humans; D007231:Infant, Newborn; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D054315:Oocyte Retrieval; D010062:Ovulation Induction / Q000009:adverse effects; D011247:Pregnancy; D018873:Pregnancy Rate; D012307:Risk Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: Assisted reproduction; birth weight; embryo cryopreservation; ovarian stimulation