Improved outcome of frozen-thawed blastocyst transfer with Menezo's two-step thawing compared to the stepwise thawing protocol.
OBJECTIVE
To compare the effects of two different blastocyst thawing protocols on implantation, pregnancy, and live birth rates.


METHODS
Ninety four consecutive frozen-thawed blastocyst transfers from 1996 to 2002 were retrospectively analyzed. Blastocysts were cryopreserved using Menezo's two-step slow freezing protocol. Frozen blastocysts were thawed for transfer according to Menezo's stepwise or two-step protocol. Immediately after thawing, assisted hatching was performed and all embryos were cultured for 3 to 5 h before transfer. Only viable embryos were selected for transfer.


RESULTS
Implantation, pregnancy (determined by the presence of fetal cardiac activity), and live birth rates were significantly higher with two-step (25, 45.7, and 42.9%) than with stepwise thawing protocol (9.2,18.6, and 16.9%, P < 0.01). The percentage of gestational sacs resulting in live babies was higher with two-step thawing (76.6%) than with stepwise thawing (50%, P = 0.04).


CONCLUSIONS
We conclude that the two-step thawing protocol offers advantages over the stepwise method. The two-step thawing protocol dramatically increased embryo implantation potential, resulting in higher pregnancy rate, and subsequent live birth rate, after frozen blastocyst transfer.
Ding
Jianchi
J
Oak Brook Fertility Center, 2425 W. 22nd Street, Suite 102, Oak Brook, Illinois 60523, USA. jding@oakbrookfertility.com
Pry
Michelle
M
Rana
Nasir
N
Dmowski
W Paul
WP
D000328:Adult; D001755:Blastocyst / Q000166:cytology / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D005615:Freezing; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies