Oocyte cryopreservation has been studied for many years without much success in refining a
method that has consistent, reliable results in producing viable embryos and clinical
pregnancies. In 1986 the first baby was born from an embryo created from a frozen oocyte;
however, since then there have been less than 150 births from frozen eggs. To date, there
are no reportable adverse outcomes in the children born from frozen oocytes. The research
continues to look at different methods of oocyte cryopreservation. Many smaller studies
have been conducted with some success but larger clinical trials are needed to replicate
these findings. The conventional cryopreservation technique has been slow cooling with
differing methods of freezing; however, vitrification is now being researched as the
potential cryopreserving method that holds some promise for the future.
Our hypothesis is the use of vitrification (quick freezing) to cryopreserve oocytes in
patients undergoing in-vitro fertilization will be more successful than slow freezing in
oocyte survival, fertilization rate with ICSI and subsequent embryo development,
implantation rate and pregnancy rate.
Cryopreservation of oocytes is desirable because it: 1) 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 to avoid
donor-recipient synchronization difficulties; and 3) can help women who may 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.
Oocyte cryopreservation using conventional slow-cooling methods has not had much success;
however more recent results have provided more optimism (Boldt et al., 2003; Porcu et al.,
1997; 2000; 2002; Yang et al., 1998; 1999; 2002; Winslow et al., 2001). Vitrification has
also been employed (Hong et al., 1999; Kuleshova et al., 1999; Yoon et al., 2000, 2003;
Chung et al 2000; Wu et al., 2001: Kuwayama et al., 2005) with increased oocyte survival
rate and live births. Vitrification is performed by suspending the oocytes in a solution
containing a high concentration of cryoprotectants and then plunging them directly into
liquid nitrogen (Rall and Fahy, 1985). The advantage of this technique is to prevent the
formation of ice crystals within the oocyte. However the toxic effect of the high
concentration of the cryoprotectant media has been a concern. New vitrification techniques
which attempt to accelerate the cooling rate by decreasing the cryosolution volume and
concentration, may reduce the potential toxicity. In addition, a more rapid cooling rate
results in reduced chilling injury (Vajta et al., 1998).
- Patients ≤ 36 years old
- Day #3 follicle stimulation hormone (FSH) < 10mIU/ml, and Estradiol < 70 pg/ml.
- The study will be limited to couples who do not wish to cryopreserve excess embryos,
who would otherwise have their excess oocytes discarded.
- Body Mass Index (BMI) ≤ 35
- Patients currently being seen in our offices
- Male partner requiring microsurgical epididymal sperm aspiration or testicular sperm
extraction (MESA/TESE) for sperm retrieval
- Day #3 follicle stimulation hormone (FSH) > 10mIU/ml, or estradiol > 70 pg/ml
- Diagnosis of Polycystic Ovary Syndrome (PCOS)
- Body Mass Index (BMI) >35
Claudio Benadiva, MD, HCLD
The Center for Advanced Reproductive Services, P.C.