Egg and Embryo Freezing
Unlike men who make sperm throughout life, women are born with all of their eggs. In fact it is estimated that at birth a woman will have 2 million eggs. This number reduces throughout life and by puberty this number has fallen to approximately 300,000! Consequently a woman’s chance of being able to conceive decreases as her age increases, especially after the age of 35. Recent scientific advances now allow a woman the option of freezing and preserving eggs.
A woman may wish to freeze her eggs for a number of reasons, both medical and social. Medically, for example, if a patient is diagnosed with cancer, she is likely to require chemotherapy or radiotherapy. These treatments will often result in infertility. If she has frozen her eggs prior to her treatment she has a chance to use these in the future, allowing her to have a baby when she would possibly not have the chance without having been able to store eggs prior to her cancer treatment.
Other women may still be waiting to meet the right partner to have children with, or wish to concentrate on their careers, and see egg freezing as a way of preserving their fertility. The chance of conception falls as a woman ages and this fall becomes dramatic after the age of 35. Sadly meaning that even with techniques as advanced as IVF successful conception may not be possible in the late 30’s or early 40’s for some women. The development of egg vitrification offers tremendous hope and now presents the option for women to opt to have eggs stored at a younger age, so preserving their fertility options. When these ladies decide they are ready to try for a baby, they have the ‘younger’ eggs stored as a back-up in case they have problems becoming pregnant on their own.
The egg freezing technique involves collecting eggs from the patient in the same way as if she was undergoing a cycle of IVF. The mature eggs are then frozen the same day. When pregnancy is desired, the eggs are thawed and fertilised via IntraCytoplasmic Sperm Injection (ICSI). Resulting embryos are then transferred to the uterus.
Egg freezing has been more of a challenge scientifically than the freezing of embryos because the egg is the largest cell in the human body and contains a lot of water. During the freezing process, this water may turn to ice crystals, which could destroy the egg. Until vitrification (a rapid freeze technique) was developed recently previous attempts at egg freezing were not very successful. However, latest published data on the new technique suggests that 99% of eggs preserved by vitrification survive and 92% fertilise successfully. Implantation rates and pregnancy rates are in keeping with women having IVF treatments at under 35 years of age. While this breakthrough is new and studies are small it offers a major advance for fertility preservation for women either for medical or social reasons. So far around 1000 babies have been born worldwide using frozen and thawed eggs. The rate of chromosomal and birth defects of these babies has been no higher than in babies born from ICSI with fresh eggs.
Embryo Vitrification Freezing
Having the ability to preserve embryos is important to our patients. Barbados Fertility Center introduced embryo vitrification in 2006. This change to the 25 year-old traditional embryo freezing technique used by most IVF units has led to our “frozen” embryo pregnancy rates being almost equal to those of our fresh embryo transfers. One of the major hurdles of traditional freezing techniques is that ice-crystal formation is VERY damaging to embryos; this hurdle had never been fully overcome until vitrification was introduced.
The damage caused by traditional freezing is one of the reasons that even the most capable IVF units rarely achieve that same results with frozen embryos as they do with fresh embryos. Vitrification works on a completely different principle for cryo-storing embryos. By suspending the embryo in a ‘glass-like’ state among high concentrations of cryoprotectants in liquid nitrogen (vitrification), we are able to avoid ice-crystal formation and offer a more reliable and successful cryopreservation of embryos.
Embryo Cryopreservation is the process by which the surplus embryos from an IVF or ICSI cycle may be stored or frozen, for use at a later date. Embryos can be frozen at a number of their developmental different stages – up to and including blastocyst stage. The Embryologist selects the embryos suitable for freezing. The embryos are then introduced into special culture media, called cryoprotectant, to help protect them during the freezing and storage process. The embryos are then frozen using a computerized embryo freezer. Once frozen, the embryos are contained within appropriately labeled sterile straws. These straws are then securely stored in a locked storage vessel immersed in liquid nitrogen ( – 196 C).Embryos can be safely stored like this for up to 5 years.
Embryo Thawing is the process by which frozen embryos are thawed with a view to placing the most suitable into the woman’s uterus. The freezing and thawing of embryos allows patients use surplus embryos from previous cycles. During thawing, the frozen embryos are warmed in a controlled manner. Once thawed the embryos are introduced back into embryo culture. The embryos are thawed the day before the embryo transfer in order that the embryo’s development can be monitored as in some cases not all embryos may survive the freeze/thaw process. On the day of transfer, our Fertility Physician Specialist performs the embryo transfer procedure. The selected embryos are introduced, through a fine catheter, into the woman’s uterus. Typically 2-3 embryos are transferred, depending on the patient’s circumstances. The embryo transfer procedure takes no more than half an hour and few women experience any discomfort.
Again, the spare embryos are then assessed in terms of their suitability to be re-frozen for use, by the couple, in future cycles. Worldwide, the success rates for frozen-thawed embryos are lower than those for fresh embryo transfers. However using Vitrification has greatly improved success rates at Barbados Fertility Center. Please contact us to receive more details on this procedure and increase your success.