title: Clinical outcomes of vitrified-thawed embryo transfer using a pull and cut straw method.
abstract: OBJECTIVE
  To compare the clinical outcomes of patients with vitrified-thawed embryos transferred using either the 0.25 mL straw method and the pull and cut straw (PNC) method. To evaluate the clinical outcomes of patients with transferred embryos that underwent assisted hatching at the cleaved embryo (day 3) or the blastocyst (day 5) stage.
  
  
  METHODS
  The study population consisted of women who underwent vitrified-warmed embryo transfer between May 2000 and December 2011 and assisted hatching was performed after warming of embryos. Cycles of thawing between assisted hatching treated and non treated groups were compared for survival and pregnancy rates.
  
  
  RESULTS
  The PNC vitrification method improved survival and pregnancy rates in partial lysed embryos. While assisted hatching did not affect the developmental and clinical pregnancy rates of the vitrified-warmed blastocyst group, it did increase the pregnancy rate of poor quality vitrified-warmed cleaved embryos.
  
  
  CONCLUSIONS
  These results suggest that PNC may increase the number of clinical pregnancies via the vitrification of both cleaved embryos and blastocysts. In addition, selective assisted hatching treatment of embryos that show a poor prognosis after warming may increase the rate of clinical pregnancy.
authors: Department of Animal Sciences, Chungbuk National University, Cheongju, Korea. ; Min Byeong Yeol Obstetrics and Gynecology, Cheongju, Korea.
authors: Joon Gyo
authors: JG
authors: Lim
authors: Young Tae
authors: YT
authors: Heo
authors: Seung Gi
authors: SG
authors: Min
authors: Byeong Yeol
authors: BY
authors: Min
authors: Sang Jun
authors: SJ
authors: Uhm
authors: Nam Hyung
authors: NH
authors: Kim
keywords: Assisted hatching; Pull and cut straw; Vitrified-thawed embryo