title: Comparison of the cryopreservation of human embryos obtained after intracytoplasmic sperm injection with a slow cooling or an ultrarapid cooling procedure.
abstract: OBJECTIVE
  Our purpose was to compare an ultrarapid method (URM) modified with dimethyl sulfoxide (Me2SO) to a slow method (SM) with propanediol (PROH) for the cryopreservation of extra human embryos in a program of intracytoplasmic sperm injection (ICSI).
  
  
  METHODS
  The extra embryos of 160 patients were cryopreserved in a prospective and randomized manner (drawing lots) by a modified URM (3 M Me2SO/0.25 M sucrose/thawing in three sucrose gradients) (Group I) or by a SM (1.5 M Propanediol/program 0-Cryologic CL863) (Group II). A total of 103 cycles has been thawed thus far. The number of thawed cycles was 58 for group I and 45 for group II.
  
  
  RESULTS
  The mean age (group I, 31.3 +/- 4.5; group II, 31.9 +/- 4.3) did not differ between the groups (P = 0.38). The number of frozen embryos (group I, 6.6 +/- 3.2; group II, 6.5 +/- 3.2) was similar (P = 0.49) for the two groups, as was the number of thawed embryos (P = 0.52) (group I, 6.5 +/- 2.9; group II, 6.2 +/- 3). The survival rate was higher (P < 0.01) for group II (83.3 +/- 23%) than for group I (69.2 +/- 28.7%). The cleavage rate was also higher (P < 0.01) for group II (56.8 +/- 31%) compared with group I (24.2 +/- 22.4%). The number of embryos transferred did not differ (P = 0.14) between the groups (group I, 3.16 +/- 1.2; group II, 3.5 +/- 1.0). The implantation rate (group I, 6.3%; group II, 13.8%) was significantly different between groups (P = 0.034). Pregnancy rates per thawed and transferred cycle were higher for group II (33.3 and 36.6%, respectively) compared with group I (13.8 and 16%, respectively), and these differences were significant (P = 0.03 and P = 0.03, respectively).
  
  
  CONCLUSIONS
  The data obtained suggest that the SM is superior to the URM for the cryopreservation of extra embryos after ICSI.
authors.affiliation: Centre for Human Reproduction, Sinhá Junqueira Maternity Foundation, Rua D. Alberto Gonçalves 1500, 14085-100, Ribeirão Preto, SP, Brazil.
authors.forename: A L
authors.initials: AL
authors.lastname: Mauri
authors.forename: C G
authors.initials: CG
authors.lastname: Petersen
authors.forename: R L
authors.initials: RL
authors.lastname: Baruffi
authors.forename: R C
authors.initials: RC
authors.lastname: Ferreira
authors.forename: J G
authors.initials: JG
authors.lastname: Franco
mesh_terms: D000328:Adult; D000367:Age Factors; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D005615:Freezing; D006801:Humans; D011247:Pregnancy; D011409:Propylene Glycols / Q000494:pharmacology; D011897:Random Allocation; D012099:Reproductive Techniques; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods*; D013997:Time Factors
chemical_list: D003451:Cryoprotective Agents; D011409:Propylene Glycols; D004121:Dimethyl Sulfoxide