title: Comparison of elective single cleavage-embryo transfer to elective single blastocyst-embryo transfer in human IVF-ET.
abstract: OBJECTIVE
  This study was carried out to compare the clinical outcome of elective single cleavage-embryo transfer (eSCET) to that of elective single blastocyst-embryo transfer (eSBET) in human IVF-ET.
  
  
  METHODS
  This study was a retrospective study which analyzed for 614 women who visited the Daegu Maria Clinic from August 2008 to December 2009. All were under 37 years old and had more than 8 mm of endometrial thickness on the day of hCG administration and at least one good quality embryo on day 3. The eSCETs were performed on day 3 (n=450) and the eSBETs were conducted on day 5 (n=164).
  
  
  RESULTS
  The numbers of retrieved oocytes, fertilized oocytes, and day 3 good quality embryos were significantly lower in the eSCET group (12.1±6.0, 8.2±4.6, and 4.2±3.1, respectively) compared to the eSBET group (16.7±7.2, 12.1±5.0, and 8.5±4.5, respectively; p<0.001). However, the clinical pregnancy, implantation, on-going pregnancy, and live birth rates of the eSCET group (46.7, 46.9, 40.0, and 36.7%, respectively) were not statistically different from those of the eSBET group (51.2, 51.8, 45.1, and 43.9%, respectively; p=0.318, 0.278, 0.254, and 0.103, respectively).
  
  
  CONCLUSIONS
  These results suggested that elective single embryo transfer should be performed regardless of the developmental stage to women less than 37 years old who had more than 8 mm of endometrial thickness on the hCG administration day and at least one good quality embryo on day 3 in order to reduce the twin pregnancy rate without reducing the whole pregnancy rate.
authors.affiliation: Daegu Maria Fertility Clinic, Daegu, Korea.
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Kang
authors.forename: Sang Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Hak Jun
authors.initials: HJ
authors.lastname: Jeong
authors.forename: San Hyun
authors.initials: SH
authors.lastname: Yoon
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Lim
authors.forename: Seong Goo
authors.initials: SG
authors.lastname: Lee