Observational clinical follow-up of oocyte cryopreservation using a slow-freezing method with 1,2-propanediol plus sucrose followed by ICSI.
BACKGROUND
The value of oocyte cryopreservation remains controversial. Two major problems exist: poor survival and injury to the oocyte meiotic spindle after freezing and thawing.


METHODS
For slow oocyte cryopreservation, we used 1.5 mol/l 1,2-propanediol and 0.3 mol/l sucrose. We waited 3 h after thawing for possible recovery of the meiotic spindles before performing ICSI.


RESULTS
Forty-three women undergoing IVF or ICSI cycles cryopreserved some or all of their harvested oocytes; of these, 20 thawed their cryopreserved oocytes for personal use and one for donation. The survival rate of oocytes after thawing was 75%, with 67% of oocytes fertilizing normally after ICSI. All 21 cycles (100%) resulted in fertilization and embryo transfers. Seven pregnancies (33%) resulted. Four women delivered five babies with normal karyotypes. Three conceptions are ongoing. Compared to 38 cycles of frozen-thawed embryos at the pronuclear stage in the same period, the percentages of survival, pregnancy and implantation were similar. Additionally, four unmarried women with white blood cell diseases underwent oocyte freezing before preconditioning treatment for haematopoietic stem cell transplantation.


CONCLUSIONS
This protocol achieved reproducible success of survival, fertilization and pregnancy for freezing and thawing of human oocytes. The 3 h post-thaw incubation could permit restoration of the meiotic spindles, thus facilitating normal fertilization.
Chen
Shee-Uan
SU
Department of Obstetrics and Gynecology, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan.
Lien
Yih-Ron
YR
Chen
Hsin-Fu
HF
Chang
Li-Jung
LJ
Tsai
Yi-Yi
YY
Yang
Yu-Shih
YS
D000328:Adult; D002470:Cell Survival; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents; D005260:Female; D005307:Fertilization in Vitro; D006402:Hematologic Diseases / Q000628:therapy; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D008297:Male; D009865:Oocytes; D011247:Pregnancy; D011256:Pregnancy Outcome; D019946:Propylene Glycol; D020554:Sperm Injections, Intracytoplasmic; D013395:Sucrose
D003451:Cryoprotective Agents; D013395:Sucrose; D019946:Propylene Glycol