Egg Freezing for Social Indications
With the trend in delayed childbearing, more single women are seeking ways to preserve their fertility potential without committing to donor sperm. Because of a newer technique called vitrification, egg freezing is now a viable alternative. Vitrification uses extremely rapid cooling rates, which causes the oocytes to be encased in a glass-like “gel” and eliminates ice formation. Recent reports of egg survival and pregnancy rates are encouraging, with the birth of thousands of children worldwide.
In January 2013 the ASRM and the SART stated that oocyte vitrification and warming should no longer be considered experimental. Studies suggest fertilization and pregnancy rates are similar to IVF/ICSI with fresh oocytes when vitrified/thawed oocytes are used as part of IVF/ICSI. In the literature, more than 90% of frozen eggs are reported to survive the thawing process and more than 70% of thawed eggs are reported to fertilize. Pregnancy rates are also encouraging, in the range of 32% to 65% per cycle. Studies are ongoing, but the current estimated birth rate per thawed egg is in the range of 4.5–12%. This means that if 10 thawed eggs were available after freezing, the likelihood of a resulting live birth would be 30 to ≥65%.
In a study of 600 donor egg recipients, there was no difference in fertilization rates (74.2% vs 73.3%), implantation rates (39.9% vs 40.9%), and pregnancy rates per transfer (55.4% vs 55.6%) between vitrified and fresh oocytes respectively.
No increase in chromosomal abnormalities, birth defects, or developmental deficits has been noted in the children born from cryopreserved oocytes to date. One study recently reported on obstetric and perinatal outcomes of 165 pregnancies and 200 infants conceived with vitrified oocytes. The multiple pregnancy rate was 17%. The mean gestational age was 37 weeks and 1 day. The rate of preterm deliveries (34–37 weeks) was 30% and the rate of preterm deliveries less than 34 weeks was 6%. The incidence of congenital anomalies was 2.5%, which is similar to the general population (estimated at 3–5%).