title: [Comparison of vitrification and slow-freezing of human day 3 cleavage stage embryos: post-vitrification development and pregnancy outcomes].
abstract: OBJECTIVE
  To compare the effects of vitrification with slow-freezing on the developmental ability of day 3 cleavage stage embryos.
  
  
  METHODS
  Patients who had no less than 4 high quality embryos were included in this study. These embryos were cryopreserved using the methods of vitrification or slow-freezing. In the cryopreserved embryo transfer cycles, the embryos which were cryopreserved using one of the methods were chosen randomly. The developmental ability of embryos was compared between these two groups.
  
  
  RESULTS
  A total of 80 patients were included in this study with 160 embryos. In the group of slow-freezing, 73 (91%) embryos were survived and achieved 15 (38%) clinical pregnancies. Among these, 3 were twins and the implantation rate was 25% (18/73). In the group of vitrification, 71 (89%) embryos were survived and achieved 19 (48%) clinical pregnancies. Among these, 9 were twins and the implantation rate was 39% (28/71), which was significantly higher than the slow-freezing group (P < 0.05). Otherwise, the clinical pregnant rate and multiple pregnant rate was higher in the group of vitrification than the slow-freezing group, but had no significance.
  
  
  CONCLUSIONS
  Vitrification is more benefit for the developmental ability of the thawed embryos and more suitable for the cryopreservation of day 3 cleavage stage embryos.
authors.affiliation: Reproductive Medical Center, Shandong Provincial Hospital, Shandong University, Jinan 250021, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
authors.forename: Zi-jiang
authors.initials: ZJ
authors.lastname: Chen
authors.forename: Hui-jun
authors.initials: HJ
authors.lastname: Yang
authors.forename: Wan-xia
authors.initials: WX
authors.lastname: Zhong
authors.forename: Shui-ying
authors.initials: SY
authors.lastname: Ma
authors.forename: Mei
authors.initials: M
authors.lastname: Li
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology / Q000502:physiology; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000379:methods*; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000166:cytology*; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D013997:Time Factors