title: Early cleavage is a valuable addition to existing embryo selection parameters: a study using single embryo transfers.
abstract: BACKGROUND
  To reduce the twin pregnancy rate, elective single embryo transfer (eSET) is increasingly implemented. Improvement of the results obtained with eSET can be achieved by better selection of the most viable embryo. This study investigated the predictive value of early cleavage (EC) as an additional parameter for selecting the embryo with the highest implantation potential by using data from SET's.
  
  
  METHODS
  Data from 165 SET's were retrospectively evaluated. Cleavage to the 2-cell stage was determined 23-26 h after injection or 25-28 h after insemination. Selection of the embryo to be transferred was based on cell morphology and cell number on the day of transfer, not on the EC status. Additional information on the predictive value of EC on developmental potential was obtained by analysing 253 transfers with two embryos (double embryo transfer, DET) and blastocyst formation of 1160 surplus embryos. Logistic regression was used to determine the predictors of pregnancy or blastocyst development.
  
  
  RESULTS
  A significantly higher pregnancy rate was observed after transfer of single EC embryos compared to single non-EC embryos (46 versus 18%). This result was confirmed by the significantly higher pregnancy rate after DET with two EC embryos as compared to DET with two non-EC embryos (45 versus 25%) and the blastocyst formation of EC embryos compared to non-EC embryos (66 versus 40%). Logistic regression showed that EC is an independent predictor for both pregnancy and blastocyst development in addition to cell morphology and cell number.
  
  
  CONCLUSIONS
  In order to improve the selection of the embryo with the highest implantation potential, selection for transfer should not be based on cell number and morphology on the day of transfer alone, but also on early cleavage status.
authors.affiliation: Research Institute Growth & Development (GROW), Department of Obstetrics & Gynaecology, Academic Hospital Maastricht, P.O.Box 5800, 6202 AZ Maastricht, The Netherlands. avmn@sgyn.azm.nl
authors.forename: Aafke P A
authors.initials: AP
authors.lastname: Van Montfoort
authors.forename: John C M
authors.initials: JC
authors.lastname: Dumoulin
authors.forename: Arnold D M
authors.initials: AD
authors.lastname: Kester
authors.forename: Johannes L H
authors.initials: JL
authors.lastname: Evers
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology; D002970:Cleavage Stage, Ovum; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000502:physiology; D047108:Embryonic Development; D005260:Female; D006801:Humans; D016015:Logistic Models; D011237:Predictive Value of Tests; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors