Oocyte Cryopreservation Comparing Fresh and Vitrified Sibling Oocytes

The necessity to cryopreserve human oocytes successfully, with the goal of achieving term pregnancies at rates equivalent to those obtained with fresh oocytes is urgent. Cryopreservation of oocytes is desirable because: 1) it would allow infertility patients to store excess oocytes instead of embryos, eliminating some of the ethical and religious concerns that accompany embryo storage; 2) permit storage of donor oocytes in egg banks, analogous to existing sperm banks. This option would allow the cryopreserved oocytes to be quarantined until screening for infectious diseases is completed, and would also avoid donor-recipient synchronization difficulties; and 3) can help cancer patients preserve their fertility before they face sterilization due to chemotherapy or radiation. Oocyte cryopreservation is therefore gaining in popularity as an option for infertility treatment as well as fertility preservation.

This is a pilot study to evaluate the outcomes of oocyte vitrification using the Cryotop method in women undergoing IVF, by simultaneously evaluating embryos derived from vitrified and fresh oocytes coming from the same stimulated cycle.

The primary outcome measures that will be tracked and tabulated are oocyte survival, fertilization and cleavage rate, and subsequent embryo development, compared between vitrified and fresh oocytes. Secondary outcomes are implantation, clinical pregnancy, miscarriage and live birth rates using embryos derived from the vitrified oocytes for transfer.

Inclusion criteria

• Females 21 to 37 years of age.
• Normal serum follicle stimulating hormone (FSH) concentration <10 mIU/ml and estradiol (E2) concentration <70 pg/ml obtained on day #2 or 3 of the menstrual cycle.
• BMI < 35.
• No physical or gynecological abnormalities (including major uterine surgery) constituting a medical contraindication to embryo transfer and pregnancy including any known significant genetic disorders
• Non-smoker for at least 3 months prior to study enrollment.
• Normal antral follicle count (total ≥ 10).

Exclusion criteria

• Greater than 1 previous miscarriage.
• More than 1 previous failed IVF attempt.
• Previous poor response to ovarian stimulation (peak E2 level <1,000 pg/ml or < 4 oocytes retrieved).
• Presence of untreated hydrosalpinx.
• Stage III or IV endometriosis.
• Intent to have preimplantation genetic diagnosis (PGD) of embryos
• Unwillingness to freeze or inseminate all eligible oocytes or embryos.
• Male partner requiring surgical sperm retrieval (MESA or TESA).