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. © 2011 The Author Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.