Embryonic Developmental Rates and Pregnancies Following the Vitrification of Human Oocytes Using Two Methodologies.

Randomization of Oocytes: Oocytes will be denuded approximately 1-2 hours post retrieval and graded for maturity. Only the Metaphase II oocyte will be vitrified. Half of the oocytes within each donor will be randomized to the following treatments.

1. Frozen using an open system using a metal grid to hold the oocyte. Three to five oocytes will be frozen on the metal grid using a minute amount (< 2-3 µls) of cryoprotectant. A top is put over the metal grid to protect the oocytes. This system has proven to be successful in limited cases in Peru. This is an open system of vitrification where the oocytes are directly plunged into liquid nitrogen. This will serve as the control.
2. Frozen in closed straws using a methodology developed by Jim Stachecki. Three to five oocytes will be frozen in ¼ cc straws. This is very similar to the method used to successfully vitrify blastocysts. This will be the experimental treatment.

Null Hypothesis: The type of vitrification methodology used will not have an impact on the following:

• Survival rates
• Embryonic developmental rates
• Pregnancy and implantation rates. Measured Outcomes The effect of vitrification technique will be measured using the appropriate statistical analysis on the following parameters.

1. Survival rates following thawing.
2. Effect of vitrification technique on how oocytes react to ICSI. The parameters have been previously defined at NCRS.
3. Normal fertilization rates, abnormal fertilization rates and rates of degeneration following ICSI.
4. Embryonic development rates. Embryos will be cultured until Day 5/6 and rate as well as quality of blastocyst will be noted.
5. Pregnancy and implantation rates following replacement in endometrial prepared recipients.