An improved protocol for dilution of cryoprotectants from vitrified human blastocysts.
BACKGROUND
The purposes of this study were to compare the survival rate of human blastocysts thawed by two different methods after vitrification using electron microscopic (EM) grids, and to report the successful pregnancies and live births resulting from the transfer of blastocysts that had survived the established thawing method.


METHODS
The blastocysts produced from three pronuclei zygotes in IVF cycles were vitrified on an EM grid. After dilution of cryoprotectant by either a 6- or 2-step method, the survival rate of the blastocysts was compared.


RESULTS
The survival rate of blastocysts thawed using the 6-step method (82.6%, 100/121) was significantly higher than that of the 2-step method (50.6%, 87/172; P < 0.01). Therefore, we applied the 6-step method in our blastocyst cryopreservation programme. Overall, 34.1% (14/41) of clinical pregnancies and 11 live births were achieved.


CONCLUSIONS
The present results indicated that a 6-step thawing method was more effective than a 2-step thawing method for thawing vitrified human blastocysts.
Cho
Hyon-Jin
HJ
In vitro Fertilization Laboratory, Maria Infertility Hospital, 103-11, Sinseol-dong, Dongdaemun-gu, Seoul, Korea.
Son
Weon-Young
WY
Yoon
San-Hyun
SH
Lee
Suk-Won
SW
Lim
Jin-Ho
JH
D001723:Birth Rate; D001755:Blastocyst / Q000502:physiology* / Q000648:ultrastructure*; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents; D005260:Female; D006801:Humans; D008854:Microscopy, Electron; D009994:Osmolar Concentration; D011247:Pregnancy; D018873:Pregnancy Rate
D003451:Cryoprotective Agents