fertility news

The practice of egg donation has come a long way since the first successful cycle in 1984. At that time the egg donor was inseminated with the recipient partner’s sperm and the resulting embryo was flushed out of the donor’s uterus and transferred to the recipient’s uterus. In today’s world concerns about sexually transmitted diseases require extensive infectious disease testing be done at least twice before any embryos are even created. And until recently only embryos created with donor eggs and partner sperm or donor sperm were used in egg donation.

Cryopreservation or freezing has been used routinely in assisted reproduction to preserve unused embryos for future use. There are two methods used to freeze embryos- one is a slow method and the other a quick freeze method known as vitrification. Vitrification is a relatively new method of cryopreservation; the first pregnancy using this method was reported in 1999.

The most recent success rates (2006) using frozen embryos to achieve pregnancy have been published by The Society for Assisted Reproductive Technology (SART) of the American Society for Reproductive Medicine (ASRM). They are as follows:

SART 2006 Clinic Summary Report. Available at: https://www.sartcorsonline.com/rptCSR_PublicMultYear.aspx?ClinicPKID=0

Although pregnancy rates are slightly lower with frozen embryos, the live birth rate using frozen embryos (like those for IVF) declines as maternal age increases due to age related changes in egg quality.

The ability to freeze human eggs for future use has not enjoyed the same success as freezing human embryos. The technique is still considered experimental but the pregnancy rates are steadily improving in particular using the vitrification method. A 2007 meta-analysis compared the slow freezing (SF) and vitrification (VF) success rates to each other and to SART data with fresh oocytes for a similar time period. They found that although SF success rates are considerably lower compared with VF and IVF with fresh oocytes, VF success rates were close to those reported by SART with fresh oocytes.

The greatest danger to the eggs occurs when they are cooled and thawed so chemicals known as cryoprotectants are used to prevent cell damage. Avoiding ice crystal formation is one of the most important goals when eggs are frozen.
Those who would benefit most from egg freezing technology include cancer patients, single women who wish to preserve their fertility and finally couples with ethical, legal or social concerns about freezing embryos. As we enter the 21st century another use for frozen eggs is emerging-donor oocyte banking for third party reproduction.

Donor oocyte banking has many advantages for patients that include:

• Reducing the time a recipient must wait for a potential donor match
• Offering recipients more potential donor choices
• Eliminating the need to synchronize the donor and recipient’s menstrual cycles

A presentation at the 2007 ASRM Annual Meeting in Washington DC supports the published information. The authors established a successful egg banking program that resulted in embryo transfers to eleven recipients. One hundred ninety-eight mature eggs were collected from 10 donors. An average of 7.8 eggs were thawed of which an average of 6.7 survived. A total of 28 embryos were transferred to the 11 recipients (2.5 embryos per recipient). Ten of the 11 patients had positive pregnancy tests. The authors concluded egg banking was an efficient way to provide high quality care in an egg donation program.

Four additional papers at the same 2007 meeting addressed concerns about the health of the children born using this technology. The news was reassuring according to Dr. Steven Ory, President of the organization at the time of the meeting. He went on to say, “Although more frozen eggs are required to establish a pregnancy than fresh eggs, frozen eggs that fertilize, develop into viable embryos and implant are as likely to result in healthy children as fresh eggs.”

In conclusion, although still the technique is still considered experimental, egg freezing is an encouraging advance in reproductive medicine and may offer egg donor recipients quicker and more efficient access to donor eggs. Preliminary studies seem to indicate good pregnancy rates can be achieved without increasing the risk of medical problems to the offspring. The technique may help some couples deal with ethical, cultural and social issues regarding whether or not to freeze their spare

Finally, as with any new technology patients need to move forward cautiously making their decision with as much information as possible. The following is a press release issued after the 2007 ASRM Annual Meeting by Marc Fritz, MD, Chair of the ASRM Practice Committee: “With any new technology it is vital that patients understand completely what the process entails and the likelihood of a successful outcome. Women contemplating the use of egg-freezing technologies need to receive extensive counseling to help them make a fully informed decision.”

References:

ASRM Practice Committee opinion: Essential elements of informed consent for elective oocyte cryopreservation. Fertil Steril 2007; 88:1495-96.

Chang C, Shapiro D, Elsner C, Mitchell-Leef D, Kort H. Clinical evaluation of the efficiency of oocyte donation program using egg cryo-banking. Fertil Steril 2007; 88: (Suppl 1): S42- S43

Homborg R, van der Veen F, Silber S. Oocyte vitrification—Women’s emancipation set in stone. Fertil Steril 2008; [E-pub ahead of print].

Jain J, Paulson R. Oocyte cryopreservation. Fertil Steril 2006; 86(Suppl 3):1037–46.

Oktay K, Cil AP, Bang H. Efficiency of oocyte cryopreservation: a meta-analysis. Fertil Steril 2006;86:70–80.

Oktay K, Pelin A, Zhang J. Who is the best candidate for oocyte cryopreservation research? Fertil Steril 2008; [E-pub ahead of print].