The Egg Freezing or Cryopreservation Process

Egg freezing or cryopreservation requires hormonal stimulation and harvesting of the eggs from the ovary through the vagina. It is imperative to perform egg freezing prior to any chemotherapy or radiation treatment as potential damage to the oocytes(eggs) can lead to a very poor ovarian response. Center for Women’s Medicine doctors reserve this option for women facing cancer treatment, or women with no partners, women who want to delay childbearing and have benign disease. Egg freezing is more challenging than embryo freezing since the freezing process may lead to damage of the cellular substructures resulting in low egg survival and low pregnancy rates.

The egg freezing program at Center for Women’s Medicine is under the direction of Dr. Dmitri Dozortsev, the IVF team utilizes the latest cryopreservation technique calledvitrification, which takes advantage of ultra-rapid cooling. This cooling is so fast that ice crystals do not have time to form when water goes inside the egg as the formation of ice crystals will induce damage to the chromosomal plate during the slow cooling stage. This technique has allowed Center for Women’s Medicine doctors to improve the frozen egg pregnancy rates without inducing irreversible damage to oocytes (eggs). Retrieved eggs can be stored for several years.

Egg freezing can be beneficial when: 

Women are undergoing certain types of reproductive surgery, chemotherapy or radiation therapy for cancer treatment. Many types of chemotherapy, as well as radiation therapy, targeting the pelvis or affecting the ovaries, may result in irreversible damage to the eggs (oocytes) contained within the ovarian follicles.  Even if those eggs do not die, their genetic material may be damaged beyond repair.

Women who have ethical concerns about producing extra embryos that may end up being discarded. The most important independent variable predictive of pregnancy during an in vitro fertilization cycle (IVF) is the number of oocytes harvested from the woman following ovarian stimulation with reproductive hormones. In most cases multiple embryos will be created in vitro, while only two or three of the best embryos will usually be transferred into the womb. The remaining embryos can either be cryopreserved or, if an embryo is of inferior quality, judged as non-viable and discarded.

Some patients do not want to create any “extra” embryos that may be potentially discarded and desire that every embryo be transferred. In such cases, only two or three eggs will be fertilized, while the remaining eggs could be frozen.

Patients want to create a bank of frozen eggs for donation (much the same as sperm bank) There are more potential egg-recipients than egg-donors. Also, a desirable egg donor may not be in the same geographical area. In such cases, being able to draw from an egg bank is a convenient option.

Women who postpone their pregnancy but desire to retain their full reproductive potential. Many women today need to postpone having children for a variety of reasons. Yet, after the age of thirty-five, a woman’s fertility begins to decline and after the age of forty pregnancy rates are very low. 

Furthermore, the chance of having a chromosomally-affected child increases exponentially between the age of forty and forty-five due to the decline in egg quality yet a women’s ability to carry the pregnancy to term is retained well past age fifty. Furthermore when eggs are frozen at age thirty and transferred at age fifty, the pregnancy rates will be that of age thirty.

A world wide data base for egg freezing outcome is ongoing. Between 1986-2008 there are close to 1000 live births with only 1.3% birth abnormalities which showed no difference when compared to congenital abnormalities occurring in naturally conceived infants. 
  

Embryo Cryopreservation

Sometimes more embryos are produced in an IVF cycle than can be safely transferred to the uterus because of the risk of high order multiple births. When extra embryos are produced, they can often be saved using the cryopreservation process. In cryopreservation, embryos are gradually “passed through” special solutions lowering their temperature until they reach the cryopreserved stage (-196 F). When the embryos are ready for use in a future IVF cycles they are very carefully, gradually thawed. Embryos can remain frozen for many years and it is believed that there is no time limit.

The Center for Women’s Medicine has a very successful embryo cryopreservation program. The advantage of using cryopreserved embryos in future cycles is that it is not necessary to undergo ovulation induction with expensive medications (FSH) thus greatly lowering the cycle cost. The female need only take medications to “synch” her body for embryo reception, using estrogen and progesterone to stimulate the endometrium and create a pregnancy like state.

IVF success rates using cryopreserved embryos are slightly less than fresh embryos but are still quite acceptable.

Learn more about egg freezing or cryopreservation by making an appointment with us by calling (713) 467 - 4488.