title: Blastocyst transfer does not cause a sex-ratio imbalance.
abstract: OBJECTIVE
  To determine whether either single or double fresh blastocyst transfers result in a sex-ratio imbalance in resulting offspring compared with transfers on day 2 or 3 and whether there is a correlation between rate of embryo development and sex of the embryo.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Large IVF center.
  
  
  METHODS
  Four hundred thirty-five live births from single fresh ETs for the period January 2005 through July 2007 and 2,043 live births from double ETs for the same period.
  
  
  METHODS
  Statistical analysis performed on sex ratio of offspring resulting from transfers (day 2, day 3, day 4, and blastocyst), as well as on the stage of development reached for each day in culture analyzed on sex of the embryo.
  
  
  METHODS
  Sex ratio of offspring by day of transfer. Stage of embryonic development by sex for each day in culture.
  
  
  RESULTS
  There was no difference in sex ratio with blastocyst transfer (single or double). There was no difference in speed of embryonic development at any stage in vitro.
  
  
  CONCLUSIONS
  Male embryos do not grow faster than female embryos in culture. Blastocyst transfer does not result in a sex-ratio imbalance in resulting offspring.
authors.affiliation: Monash IVF, Monash University, Clayton, Victoria, Australia; Centre for Women's Health Research, Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia. Electronic address: gareth.weston@med.monash.edu.au.
authors.forename: Gareth
authors.initials: G
authors.lastname: Weston
authors.affiliation: Monash IVF, Monash University, Clayton, Victoria, Australia.
authors.forename: Tiki
authors.initials: T
authors.lastname: Osianlis
authors.affiliation: Monash IVF, Monash University, Clayton, Victoria, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Catt
authors.affiliation: Monash IVF, Monash University, Clayton, Victoria, Australia; Centre for Women's Health Research, Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia.
authors.forename: Beverley
authors.initials: B
authors.lastname: Vollenhoven
mesh_terms: D002970:Cleavage Stage, Ovum / Q000502:physiology; D046149:Embryo Culture Techniques; D004624:Embryo Transfer / Q000009:adverse effects* / Q000379:methods; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology; D047108:Embryonic Development / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D007231:Infant, Newborn; D050498:Live Birth; D008297:Male; D011247:Pregnancy; D019836:Preimplantation Diagnosis; D012189:Retrospective Studies; D012727:Sex Characteristics; D012743:Sex Preselection; D012744:Sex Ratio