title: Laser-assisted hatching increases pregnancy and implantation rates in cryopreserved embryos that were allowed to cleave in vitro after thawing: a prospective randomized study.
abstract: BACKGROUND
  Cryopreservation of embryos may lead to zona hardening that may compromise in vivo hatching and implantation following thawing and transfer. Assisted hatching (AH) has been advocated as a means of assisting the natural hatching process and enhancing implantation.
  
  
  METHODS
  The aim of this study was to assess in a prospective randomized manner the effect of laser-assisted hatching (LAH) on implantation as well as clinical and multiple pregnancy rates (the primary outcome) after the transfer of frozen-thawed embryos. All embryos were thawed the day before transfer, and LAH was performed the next day on embryos that cleaved. Control group consisted of embryos that were transferred without AH.
  
  
  RESULTS
  The performance of LAH significantly increased implantation (9.9 versus 20.1%, P < 0.01), clinical pregnancy (27.3 versus 40.9, P < 0.05) and multiple pregnancy rates (16 versus 40.3%, P < 0.07). In the LAH group, significantly more excess embryos that were left in culture hatched in vitro.
  
  
  CONCLUSIONS
  LAH improves the outcome of frozen-thawed embryo transfer when performed before transfer on embryos that were allowed to cleave.
authors.affiliation: Assisted Reproduction Unit, American Hospital of Istanbul, Istanbul, Turkey.
authors.forename: Basak
authors.initials: B
authors.lastname: Balaban
authors.forename: Bulent
authors.initials: B
authors.lastname: Urman
authors.forename: Kayhan
authors.initials: K
authors.lastname: Yakin
authors.forename: Aycan
authors.initials: A
authors.lastname: Isiklar
mesh_terms: D015925:Cryopreservation; D010064:Embryo Implantation / Q000528:radiation effects; D004622:Embryo, Mammalian / Q000528:radiation effects; D005260:Female; D006801:Humans; D053685:Laser Therapy; D011247:Pregnancy; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic