Mar 21, 2011
At long last, it seems, it has become possible to successfully freeze (and thaw) human eggs. Vitrification, a process of freezing living tissue has been an elusive goal for researchers hoping to preserve human oocytes. Recently however, the University of Connecticut Health Center has reported a series of 6 live births from eggs that have been frozen and thawed. They join several other centers that are also reporting success. UCHC will begin an egg donation program this summer. Their technique is one of several new safe and effective options for oocyte cryo-preservation. Egg freezing, which has previously been considered only experimental may soon become widespread.
Until very recently, for women, the biological clock has continued relentlessly ticking. Despite significant advances in assisted reproductive technologies, women over 40 have a small chance and beyond age 45, women have almost no hope of achieving a successful live birth using their own eggs. New methods of oocyte cryopreservation, will very likely change this, however, allowing women to better correlate their fertility desires with the career and relationship demands of today. Women with cancer or other conditions necessitating chemo or radiation therapy, probably represent the most important group for whom this technology is being developed. These women may now choose to freeze and store eggs, circumventing infertility which commonly otherwise occurs as a consequence of treatment.
Assisted reproductive technology(ART) has a long and colorful history. The first successful pregnancy resulting from artificial insemination (AI) was described in 1790. The next significant advance was not reported until 1953 when a pregnancy resulting from a frozen sperm was achieved. sperm donation and banking has since become well accepted and widely practiced. In vitro (test tube) fertilization was originally developed as a solution for women with "tubal factor" infertility. When normally fertile couples conceive, egg and sperm meet in the fallopian tube, the fertilized egg or embryo subsequently navigates onward through the tube and ultimately implants in the endometrium (uterine lining). Endometriosis, sexually transmitted infections or surgical scarring can cause tubal blockages which interrupt this sequence of events.
The very first successful in vitro fertilization (IVF) of a human ova in 1973 resulted in a chemical pregnancy. The second, in 1976, an ectopic pregnancy. Finally in 1978 Louise Brown was born. Her successful conception was achieved through a process developed by Drs. Steptoe and Edwards. Because continued refinements in IVF technologies have now made it so successful, often more embryos than are needed result from a cycle; often as many as 20 eggs fertilize. Freezing the extra embryos was a logical next step. Interestingly, freezing and thawing embryos is much easier to do than vitrification. Genetically more stable, than ova, embryos frozen for as long as 20 years have been thawed, transferred, and ultimately born.
For a woman without a male partner to fertilize her eggs however,"freezer burn" until now has forestalled further progress. As opposed to men who are continually manufacturing new sperm cells, women are born with their ovaries "preloaded" with eggs. At birth, a woman's ovaries have about 2 million eggs. At puberty only about 400,000 remain. By the average age of menopause, 50, there will be only approximately 1000 remaining. Not only are eggs lost to atresia, but as they age, they suffer wear and tear. The delicate machinery that allows an egg to divide its chromosomes properly in half, breaks down over time. Abnormal numbers of chromosomes in an egg result in embryos which may not implant, may miscarry, or may result in the birth of a child with problems such as Down's syndrome. By the time a woman is 45, her risk of having a child with Down's syndrome reaches 1/30 live births. Her risk of all types of chromosomally-mediated birth defects is approx 1/10.
It seems possible that at last persistent "tweaking" of the vitrification procedure has finally paid off. UConn's first successful live birth from an egg which was frozen, reported in 2002, has now been succeeded by 5 more babies.
Worldwide, over 900 babies have been born following oocyte cryopreservation. UConn will begin an egg freezing program this summer. Initially their goal is to permit women needing cancer treatment to store their eggs for the future when improved health may permit pregnancy. Soon, many healthy women may have the opportunity to take advantage of this promising new technology. Already we are beginning to see egg and sperm banks side by side. For more information on UConn's program see: