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Updated: Jul 22, 2026
Cryopreservation of Preimplantation Embryos of Cattle, Sheep, and Goats
Published on: August 5, 2011
Assisted hatching improves implantation rates on cryopreserved-thawed embryos. A randomized prospective study
A Gabrielsen1, I Agerholm, B Toft
1Ciconia Fertility Clinic, Aarhus, DK-8270 Højbjerg, Denmark. ag@ciconia.dk
Background:
Focus on the hatching process has so far been in the field of fresh embryos. Cryopreserved-thawed embryos have a lower rate of pregnancy than fresh embryos, which might be due to hardening of the zona pellucida.
Methods:
During a 2 year period, a prospective randomized study enrolling 253 cryopreserved-thawed cycles was performed on day 2 embryos. Pseudorandomization to assisted hatching or a control group was done on the basis of even and odd dates for thawing. One hour before embryo transfer, hatching was carried out using acidic Tyrode's solution.
Results:
Among 136 embryos exposed to assisted hatching, 11.4% (30) were implanted compared with only 5.8% (13) of 117 embryos not exposed to assisted hatching (P<0.05, chi(2) test). No difference in the rate of clinical pregnancy and positive serum HCG was observed between the two groups. Very few women >38 years old were included in the study, and no significant difference according to age could be found between the groups.
Conclusions:
These results show that assisted hatching using acidic Tyrode's solution increases the implantation rate of cryopreserved-thawed embryos (P<0.05).
