title: A pragmatic RCT of conventional versus increased concentration sucrose in freezing and thawing solutions for human embryos.
abstract: BACKGROUND
  Intact frozen-thawed embryos have a greater potential than damaged embryos to establish successful pregnancies. This study aimed to determine whether elevated concentrations of sucrose during freezing would increase the proportion of patients with ≥ 50% of embryos intact after thawing (primary outcome), and improve clinical outcome.
  
  
  METHODS
  In a two arm, parallel group, pragmatic trial, IVF/ICSI couples were randomized prospectively to have their supernumerary embryos frozen in a medium containing 0.1 M sucrose (control; n = 99) or 0.3 M sucrose (intervention; n = 102).
  
  
  RESULTS
  More control (74/99) than intervention (63/102) couples had at least one embryo thawed (P = 0.07). Significantly more (P = 0.005) intervention (53/63) than control (45/74) couples had ≥ 50% of embryos intact. Freezing in a medium containing 0.3 M sucrose increased by 3.4-fold [95% confidence interval (CI) (1.45, 7.82)] the likelihood of a couple having ≥ 50% of their embryos intact. In the fresh cycle, live birth rate per transfer was similar in the control (35/95) and intervention (36/93) groups (P = 0.91). More control (19/63) than intervention (9/59) couples had a live birth after frozen embryo transfer (P = 0.08). When fresh and frozen cycles were combined, fewer intervention (n = 102) than control (n = 99) couples had at least one live birth (42 versus 53%). The difference in cumulative live birth rate was not significant [hazard ratio = 0.75, 95% CI (0.49, 1.13); P = 0.17].
  
  
  CONCLUSIONS
  Increasing the concentration of sucrose in the freezing medium improves embryo survival, but this is not reflected by increased cumulative birth rates.
  
  
  BACKGROUND
  ISRCTN93314892.
authors.affiliation: Division of Applied Health Sciences, University of Aberdeen, Aberdeen, UK. maureen.wood@abdn.ac.uk
authors.forename: M J
authors.initials: MJ
authors.lastname: Wood
authors.forename: J
authors.initials: J
authors.lastname: Mollison
authors.forename: K
authors.initials: K
authors.lastname: Harrild
authors.forename: E
authors.initials: E
authors.lastname: Ferguson
authors.forename: T
authors.initials: T
authors.lastname: McKay
authors.forename: A
authors.initials: A
authors.lastname: Srikantharajah
authors.forename: L
authors.initials: L
authors.lastname: Bell
authors.forename: S
authors.initials: S
authors.lastname: Bhattacharya
mesh_terms: D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000187:drug effects*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D050498:Live Birth; D011247:Pregnancy; D011256:Pregnancy Outcome; D020554:Sperm Injections, Intracytoplasmic; D013395:Sucrose / Q000008:administration & dosage*
chemical_list: D003451:Cryoprotective Agents; D013395:Sucrose