A randomized controlled trial comparing two vitrification methods versus slow-freezing for cryopreservation of human cleavage stage embryos

Giovanna Fasano & Nicolas Fontenelle &

Anne-Sophie Vannin & Jamila Biramane &

Fabienne Devreker & Yvon Englert & Anne Delbaere

Abstract

Purpose To compare two different vitrification methods to

slow freezing method for cryopreservation of human cleavage

stage embryos. Design: Prospective randomised trial. Setting:

University assisted reproduction centre. Patient(s): 568 patients

(mean age 33.4±5.2) from April 2009 to April 2011.

Methods 1798 supernumerary good-quality cleavage stage

embryos in 645 IVF cycles intended to be cryopreserved were

randomly allocated to three groups: slow freezing, vitrification

with the Irvine® method, vitrification with the Vitrolife®

method. Main Outcome Measure(s): Embryo survival and

cleavage rates, implantation rate.

Results A total of 1055 embryos were warmed, 836 (79.2 %)

survived and 676 were finally transferred (64.1 %). Postwarming

embryos survival rate was significantly higher after

vitrification (Irvine: 89.4 %; Vitrolife: 87.6 %) than after slow

freezing (63.8 %) (p <0.001). No differences in survival rates

were observed between the two vitrification methods, but a

significant higher cleavage rate was observed using Irvine

compared to Vitrolife method (p <0.05). Implantation rate

(IR) per embryo replaced and per embryo warmed were

respectively 15.8 % (41/259) and 12.4 % (41/330) for

Irvine, 17.0 % (40/235) and 12.1 % (40/330) for Vitrolife,

21.4 % (39/182) and 9.9 % (39/395) for slow-freezing (NS).

Conclusions Both vitrification methods (Irvine and Vitrolife)

are more efficient than slow freezing for cryopreservation of

human cleavage stage embryos in terms of post-warming

survival rate. No significant difference in the implantation rate

was observed between the three cryopreservation methods.

Keywords Human cleavage stage embryo . Vitrification .

Slowfreezing .Survival andcleavage rates .Clinical outcomes

Results

Results from the 1055 warmed embryos are summarised in

Table 1. Post-warming survival of embryos in both vitrification

methods were significantly higher compared to slow-freezing

(p <0.001). The proportion of embryos with 100 % intact

blastomeres after warming was significantly higher after vitrification

than after slow-freezing (p <0.001). The cleavage rates

of survived embryos after warming were significantly higher

with vitrification methods (Irvine: p <0.001; Vitrolife: p <0.05

respectively) compared to slow-freezing. A significant

difference in cleavage rate was observed between the two

vitrification methods (p <0.05) (Table 1).

Due to the higher post-warming survival and cleavage rate

of embryos, significantly more transfers per warming cycle

were performed when embryos were cryopreserved by both

vitrification methods compared to slow-freezing method

(p <0.001). As summarised in Table 2, significant difference

in the transfer rates per warming cycle was observed between

the two vitrification methods (p <0.05) (Table 2).

Implantation rate (IR) per embryo transferred and per embryo

warmed and live birth (LB) per transferred embryo and

per warmed embryo were no significant different (NS) between

the three cryopreservation methods in the results obtained

on the study sample (Table 1).

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