title: Comparison of the sex ratio with blastocyst transfer and cleavage stage transfer.
abstract: OBJECTIVE
  To evaluate the sex ratio in births conceived with blastocyst transfer compared to day 3-ET.
  
  
  METHODS
  A retrospective analysis of IVF patients who became pregnant after blastocyst or cleavage stage transfer at Stanford University Hospital and a literature review were performed.
  
  
  RESULTS
  In the day 3-ET group, the male-to-female (M/F) ratio was 157/139 (53%/47%) compared to 97/66 (59.5%/40.5%) in the blastocyst group (P = 0.18). Similar trends have been found in individual studies in the literature but reached statistical significance in only one out of six reports reviewed. The combined data from our study and the literature show a male-to-female ratio of 797/594 (57.3%/42.7%) in blastocyst transfer compared to 977/932 (51.2%/48.8%) in day 3-ET (P = 0.001).
  
  
  CONCLUSIONS
  Although individual studies may lack power to show an altered sex ratio with blastocyst transfer, the combined data presented in this report do suggest that the M/F ratio is higher with blastocyst transfer compared to cleavage stage transfer.
authors.affiliation: Department of Gynecology and Obstetrics, Stanford University School of Medicine, Stanford, California 94305, USA. milki4@aol.com
authors.forename: Amin A
authors.initials: AA
authors.lastname: Milki
authors.forename: Sunny H
authors.initials: SH
authors.lastname: Jun
authors.forename: Mary D
authors.initials: MD
authors.lastname: Hinckley
authors.forename: Lynn W
authors.initials: LW
authors.lastname: Westphal
authors.forename: Linda C
authors.initials: LC
authors.lastname: Giudice
authors.forename: Barry
authors.initials: B
authors.lastname: Behr
mesh_terms: D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D012189:Retrospective Studies; D012744:Sex Ratio