title: Vitrification of human blastocysts using cryoloops: clinical outcome of 223 cycles.
abstract: BACKGROUND
  The need to cryopreserve human blastocysts is increasing. The successful birth has been reported of a baby from a blastocyst vitrified using the cryoloop technique. The present study expands on this earlier report to confirm the effectiveness of this vitrification procedure.
  
  
  METHODS
  In patients undergoing IVF at one of three clinics, supernumerary blastocysts on day 5 or 6 at various stages of development were vitrified using cryoloops.
  
  
  RESULTS
  Of 725 vitrified blastocysts, 583 (80.4%) survived. After the transfer of 493 blastocysts in 207 cycles, 76 women (37%) became clinically pregnant. Among these women, 21 pregnancies ended in miscarriage, 23 healthy babies were born in 18 deliveries, and 37 pregnancies are ongoing. The survival rate of day 5 blastocysts (87%) was higher than that of day 6 blastocysts (55%), but implantation rates and pregnancy rates were not statistically significantly different.
  
  
  CONCLUSIONS
  Clinical outcomes with 725 blastocysts and 207 transfers showed that vitrification using cryoloops is effective and practical for the cryopreservation of human blastocysts. Early blastocysts on day 5 seem to be the most suitable in terms of stage and age for cryopreservation, but developed and day 6 blastocysts can also be cryopreserved.
authors.affiliation: Hiroshima HART Clinic, 5-7-10 Ohtemchi, Naka-ku, Hiroshima, Osaka HART Clinic, Snowcrystal 10F 2-6-20, Umeda, Kita-ku, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Mukaida
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
authors.forename: T
authors.initials: T
authors.lastname: Tomiyama
authors.forename: S
authors.initials: S
authors.lastname: Wada
authors.forename: C
authors.initials: C
authors.lastname: Oka
authors.forename: M
authors.initials: M
authors.lastname: Kasai
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D013997:Time Factors; D016896:Treatment Outcome