In 2005, a study was published that compared and examined the success rates for frozen and unfrozen oocytes. Parameters under study included live birth rates, clinical pregnancy, and implantation rates. In vitro fertilization success rates with slow-frozen oocytes were significantly lower when compared with in-vitro fertilization success rates for oocytes that had not been frozen. The researchers felt that further studies needed to be conducted to determine this technique’s efficiency and safety.
In May 2013, researchers from New York Medical College and the University of California at Davis tabulated age-specific probabilities of live births after in-vitro fertilization (IVF) using frozen eggs. This study was a meta-analysis of oocyte cryopreservation cycles utilizing patient data, which reported the probability of live birth resulting from IVF cycles.
Although in-vitro fertilization has been utilized extensively in infertility cases, egg freezing is a relatively recent technique. This elective procedure enables women to preserve their fertility, enabling them to have future opportunities for bearing children. Until now, women who had undergone oocyte cryopreservation could not predict their chances of a live birth once the embryos were transferred.
By collecting and using raw data from ten previously published studies on oocyte cryopreservation, the researchers could amass the world’s largest database on pregnancy outcomes after this procedure.
The database included data from 2,265 egg freezing cycles in 1,805 women in Europe and the U.S. The amount of data was sufficient enough to allow the researchers to generate and extrapolate numerical values to be used to determine egg freezing success rates based on such factors as a patient’s age, number of oocytes frozen, and the method of egg freezing used, whether it be slow freezing or vitrification.
This study allows for the utility of a live pregnancy rate estimator that can be used to calculate and predict individual chances for live births. Using the estimates provided, women can make a well-informed decision about undergoing the elective egg freezing procedure independently or in addition to an IVF cycle.
As expected, the study underscored that egg freezing success rates decline with age. However, the drop in success rates continues more sharply for women older than 36. Pregnancies can, however, result from the transfer and implantation of previously frozen eggs in patients as old as 44 years of age, but the success rates are less optimistic after age 42.