Vitrification of oocytes produces high pregnancy rates when carried out in fertile women

Objective

To determine the efficiency of our vitrification technique when applied in young fertile women.

Design

Clinical research and application.

Setting

In vitro fertilization center.

Patient(s)

Twenty-one women were recruited from the navy community with 19 patients finishing the study.

Intervention(s)

Vitrified oocytes with use of the electron microscopic grid method were warmed 6 months after vitrification. Surviving metaphase II oocytes were microinjected for fertilization, and clinical results were evaluated.

Main Outcome Measure(s)

Survival, fertilization, and cleavage rate. Pregnancy and implantation rate.

Result(s)

Three hundred ninety-five oocytes were warmed, of which 320 oocytes (81.0%) survived. Two hundred eighty-five metaphase II oocytes were microinjected for fertilization; 206 of them (72.3%) fertilized, and 53 embryos were transferred to 19 patients (in 20 warming cycles). Twenty-four of 53 transferred embryos (45.3%) implanted as confirmed by ultrasound examination. Of the 20 transfers, 16 resulted in clinical pregnancy (80%), 3 miscarried (15%), and 13 (65%) went on to produce 20 live births, respectively. This is much higher in comparison with our previous data using supernumerary oocytes where the rates of implantation and pregnancy were 6% and 21%. Live-birth rates per warmed oocyte and per injected oocyte were 5.1% and 7.2%, respectively.

Conclusion(s)

High pregnancy and implantation rates were observed after 6 months of cryopreservation by vitrification when oocytes from fertile woman were used. Proper screening of candidates for oocyte cryopreservation is of crucial importance to assure a favorable pregnancy outcome.

Key Words: Human oocyte cryopreservation, vitrification, electron microscope grid, ethylene glycol, clinical outcome