Test tube pregnancy less likely with frozen eggs

In vitro fertilization (IVF), a popular type of test tube fertility technique, is less likely be successful in the mother's eggs have been frozen and stored, researchers report in the journal Fertility and Sterility.

With IVF, the egg is fertilized by the sperm outside the body and the resulting embryo is placed in the mother. The egg may be relatively fresh or it may have been obtained in the past and frozen until ready for use. This latter approach allows women with certain cancers and other diseases to save some of their eggs before receiving toxic therapies that could shut down their ovaries for good.

Almost two decades have passed since frozen eggs were first used with IVF, Dr. Kutluk Oktay, from Weill Medical College of Cornell University, New York and colleagues comment in their article. Yet, how this approach compares with the use of unfrozen eggs still remains unknown.

The researchers conducted an analysis of data from 26 studies released between January 1997 and June 2005 that looked at the outcomes of IVF with frozen eggs. These results were then compared with the researchers' results using unfrozen eggs in 2002 and 2003.

The likelihood of one sperm-injected egg ultimately becoming a live infant was 6.6 percent using unfrozen eggs. While this rate may seem low, with frozen eggs the rate was just 3.4 percent.

For each embryo that is successfully generated with frozen and unfrozen eggs, the live birth rates were 21.6 and 60.4 percent, respectively.

IVF with frozen eggs "appears to justify its use to preserve fertility" in young women who will be receiving medical treatments that can destroy their ability to produce eggs, the authors conclude. However, "its value for elective applications remains to be determined."

SOURCE: Fertility and Sterility, July 2006.