A pragmatic randomised controlled trial of conventional versus increased concentration sucrose in freezing and thawing solutions for human embryos

Maureen Wood, Jill Ann Mollison, Kirsten Ann Harrild, Elizabeth Ferguson, Thelma McKay, Arasaratnam Srikantharajah, Lorna Margaret Bell, Siladitya Bhattacharya

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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.
Original languageEnglish
Pages (from-to)1987-1996
Number of pages10
JournalHuman Reproduction
Issue number8
Early online date16 May 2011
Publication statusPublished - 2011



  • freezing
  • embryo
  • sucrose
  • prospective RCT
  • cumulative live birth

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