Fertilization and in vitro development of cryopreserved human prophase I oocytes.

OBJECTIVE

To determine the potential for in vitro maturation, fertilization, and cleavage after cryopreservation of immature, prophase I human oocytes.

DESIGN

Immature oocytes obtained in excess of the number required by the patient were randomized and cryopreserved at the prophase I stage or cultured as control. After thawing and maturation in vitro, test and control oocytes were inseminated with husband's sperm and evaluated for fertilization and cleavage in vitro.

SETTING

In vitro fertilization program.

PATIENTS: Consenting patients undergoing controlled ovarian hyperstimulation for the purposes of IVF.

MAIN OUTCOME MEASURES: Rates of maturation to metaphase II, fertilization, and cleavage were compared between control and cryopreserved oocytes.

RESULTS

Upon thaw, 58.5% (72/123) of prophase I oocytes were viable. Control oocytes demonstrated a 74.8% (98/131) maturation rate to metaphase II, a 56.5% (52/92) fertilization rate, and an 11.5% (6/52) blastocyst rate. Cryopreserved oocytes showed a 83.3% (60/72) rate of maturation, a 57.7% (30/52) fertilization rate, and a 3.3% (1/30) blastocyst rate. No significant differences were noted between any of these parameters.

CONCLUSIONS

These results demonstrate that prophase I oocytes from stimulated IVF cycles are able to survive cryopreservation and resume meiosis to achieve full nuclear maturation post-thaw. In addition, cryopreserved oocytes retain the same capacity for fertilization and development as control oocytes.