title: Artificial shrinkage of blastocysts prior to vitrification improves pregnancy outcome: analysis of 1028 consecutive warming cycles.
abstract: OBJECTIVE
  This study aims to compare implantation, pregnancy, and delivery rates in frozen transfer cycles with blastocysts that were vitrified either with artificial shrinking (AS group) or without (NAS group).
  
  
  METHODS
  Retrospective comparative study of artificial shrinking of blastocysts prior to vitrification and frozen embryo transfer cycles in infertile patients undergoing frozen embryo transfer (FET) was done at the Humanitas Fertility Center between October 2009 and December 2013. Main outcome measure(s) were implantation (IR), pregnancy (PR), and delivery rates (DR) between the two groups.
  
  
  RESULTS
  A total of 1028 consecutive warming blastocyst transfer cycles were considered. In 580 cycles (total of 822 blastocysts), artificial shrinking was performed prior to vitrification (AS group), while in the remaining 448 cycles (total of 625 blastocysts), the artificial shrinking was not performed (NAS group). There were no differences in patient age (36.4 ± 3.7 vs. 36.3 ± 3.9) and number of embryos transferred (1.41 ± 0.49 vs. 1.38 ± 0.50) between groups. The IR, PR, and DR in the AS group were significantly higher (p < 0.05) than in the NAS group (29.9 vs. 23.0 %, 36.3 vs. 27.9 %, and 26.5 vs. 18.1 %, respectively).
  
  
  CONCLUSIONS
  Performing AS of blastocysts prior to vitrification appears to improve implantation, pregnancy, and delivery rates probably related to a decreased risk of ultrastructural cryodamages, plausible when cryopreserving expanded blastocysts.
authors.affiliation: Humanitas Fertility Center, Department of Gynaecology, Division of Gynaecology and Reproductive Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy. paolo.levi_setti@humanitas.it.
authors.forename: Paolo Emanuele
authors.initials: PE
authors.lastname: Levi-Setti
authors.affiliation: Humanitas Fertility Center, Department of Gynaecology, Division of Gynaecology and Reproductive Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Menduni
authors.affiliation: Humanitas Fertility Center, Department of Gynaecology, Division of Gynaecology and Reproductive Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Smeraldi
authors.affiliation: Department of Obstetrics, Gynaecology and Reproductive Sciences, School of Medicine, Yale University, New Haven, CT, USA.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Patrizio
authors.affiliation: Biostatistics Unit, Humanitas Research Hospital, Rozzano, Milan, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Morenghi
authors.affiliation: Humanitas Fertility Center, Department of Gynaecology, Division of Gynaecology and Reproductive Medicine, Humanitas Research Hospital, Rozzano, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Albani
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation; D046149:Embryo Culture Techniques / Q000379:methods*; D010064:Embryo Implantation / Q000502:physiology; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D027724:Reproductive Techniques, Assisted; D058989:Vitrification
keywords: Artificial shrinkage; Blastocyst; Cryopreservation; Frozen embryo transfer