Vitrification versus slow freezing gives excellent survival, post warming embryo morphology and pregnancy outcomes for human cleaved embryos.
OBJECTIVE
The objective of this retrospective study was to evaluate the efficacy of vitrification and slow freezing for the cryopreservation of human cleavage stage embryos in terms of post-warming survival rate, post-warming embryo morphology and clinical outcomes.


METHODS
The embryos of 305 patients at cleavage stages were cryopreserved either with vitrification (153 patients) or slow-freezing (152 patients) methods. After warming; the survival rate, post-warmed embryo morphology, clinical pregnancy and implantation rates were evaluated and compared between the two groups.


RESULTS
In the vitrification group versus slow freezing group, the survival rate (96.9% vs. 82.8%) and the post-warmed excellent morphology with all blastomeres intact (91.8% vs. 56.2%) were higher with an odds ratio of 6.607 (95% confidence interval; 4.184-10.434) and 8.769 (95% confidence interval; 6.460-11.904), respectively. In this group, the clinical pregnancy rate (40.5% vs. 21.4%) and the implantation rate (16.6% vs. 6.8%) were also higher with an odds ratio of 2.427 (95%confidence interval; 1.461-4.033) and 2.726 (95% confidence interval; 1.837-4.046), respectively.


CONCLUSIONS
Vitrification in contrast to slow freezing is an efficient method for cryopreservation of human cleavage stage embryos. Vitrification provides a higher survival rate, minimal deleterious effects on post-warming embryo morphology and it can improve clinical outcomes.
Rezazadeh Valojerdi
Mojtaba
M
Embryology Department, Reproductive Medicine Research Center, Royan Institute, ACECR, 19395-4644, Tehran, Iran. mr_valojerdi@yahoo.com
Eftekhari-Yazdi
Poopak
P
Karimian
Leila
L
Hassani
Fatemeh
F
Movaghar
Bahar
B
D000328:Adult; D015925:Cryopreservation / Q000379:methods*; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D004622:Embryo, Mammalian; D005260:Female; D005615:Freezing; D006801:Humans; D010062:Ovulation Induction; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies