Transfer of frozen-thawed blastocysts that underwent quarter laser-assisted hatching at the day 3 cleaving stage before freezing.
OBJECTIVE
To examine the pregnancy potential of frozen-thawed blastocysts that underwent quarter laser-assisted hatching (AH) at the cleaving stage before freezing and to compare clinical and embryo characteristics between the groups that succeeded in and failed to achieve pregnancy.


METHODS
Prospective observational study.


METHODS
Thirty-four of 112 patients with frozen blastocysts requiring transfer of thawed embryos between January 2000 and December 2001.


METHODS
Assisted reproductive technology unit in a tertiary medical center.


METHODS
Embryos of patients undergoing blastocyst transfers routinely underwent quarter AH using a nontouch 1.48-microm diode laser. Blastocysts not transferred were cryopreserved using a six-step freezing protocol with glycerol as the cryoprotectant.


METHODS
Postthaw embryo survival and zona pellucida (ZP) maintenance, implantation rate, and clinical pregnancy rate per transfer of thawed blastocysts.


RESULTS
A total of 118 frozen blastocysts was thawed. Of these, 89 (75.4%) embryos survived and were transferred in 35 cycles. Assisted hatching-manipulated ZP tolerated the freeze-thaw procedures without shape distortion in surviving embryos. Eleven (31.4%) clinical pregnancies with 15 intrauterine gestational sacs occurred, for an implantation rate of 16.9%. Those who succeeded in pregnancy tended to have more embryos available before freezing, more original blastocysts of good quality for freezing, and more surviving blastocysts after thawing for transfer than did those who failed to achieve pregnancy.


CONCLUSIONS
An acceptable clinical pregnancy rate was obtained from transfer of thawed blastocysts that underwent laser AH on the ZP at the day 3 cleaving embryo stage in fresh cycles in selected patients. Embryo characteristics before freezing played major roles in determining implantation potential of thawed embryos.
Kung
Fu-Tsai
FT
Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
Lin
Yi-Chi
YC
Tseng
Ya-Jung
YJ
Huang
Fu-Jeng
FJ
Tsai
Meng-Ying
MY
Chang
Shiuh-Young
SY
D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007834:Lasers; D008297:Male; D010062:Ovulation Induction / Q000379:methods; D011247:Pregnancy; D011446:Prospective Studies; D015044:Zona Pellucida / Q000502:physiology