E. Flisser

Blastocyst vitrification, cryostorage and warming does not affect live birth rate, infant birth weight or timing of delivery

RESEARCH QUESTION Does vitrification and warming affect live birth rate, infant birth weight and timing of delivery? DESIGN Retrospective, cohort study comparing outcomes of donor oocyte recipient fresh (n = 25) versus vitrified (n = 86) euploid blastocyst transfers; donor oocyte recipient singleton live births from fresh (n = 100) versus vitrified (n = 102) single embryo transfers (SET); and autologous vitrified euploid SET (n = 1760) (cryostored 21-1671 days). RESULTS Group 1: fresh and vitrified-warmed blastocysts had similar live birth (OR 1.7; 95% CI 0.5 to 5.9), implantation (OR 0.9; 95% CI 0.2 to 3.9), clinical pregnancy (OR 3.4; 95% CI 0.9 to 13.0) and pregnancy loss (OR 1.2; 95% CI 0.98 to 1.4); group 2: low birth weight (OR 0.44; 95% CI 0.1 to 1.6) and preterm delivery (0.99; 95% CI 0.4 to 2.3) rates were similar in fresh and vitrified-warmed blastocyst transfers; group 3: cryostorage duration did not affect live birth (OR 1.0; 95% CI 1.0 to 1.0), implantation (OR 1.0; 95% CI 0.99 to 1.01), clinical pregnancy (OR 1.0; 95% CI 1.0 to 1.0]), pregnancy loss (OR 0.99; 95% CI 1.0 to 1.0), birth weight (β = -15.7) or gestational age at delivery (β = -0.996). CONCLUSIONS Vitrification and cryostorage (up to 4 years) are safe and effective practices that do not significantly affect clinical outcome after embryo transfer.