Fertility preservation is enabling many women to make reproductive choices that fit their lives. Preserving fertility when it is optimal, for later use, provides an option for later fertility1.
If having a child now is not the right choice, what are the options? What are the limits to this technology? Who can benefit, and when should egg freezing be done? How long can a woman wait before pursuing fertility preservation? These are all important questions with answers starting to emerge.
Pacific Fertility Center is a pioneer in vitrification, the best technology available today for fertility preservation. Different from egg freezing, vitrification is an ultra-rapid cooling process that results in a phase change of the oocyte. The fluids in the egg turn to a solid state without the crystallization of slower freezing techniques. Avoiding freezing is critical to maintaining good outcomes with fertility preservation.
Best outcomes with fertility preservation are found when a woman is young. Under age 30, the eggs are of high quality, and are high in number. A typical treatment of fertility preservation in a woman under age 30 will yield 12-18 oocytes, enough to produce 3-5 quality embryos and a good chance of later pregnancy, and perhaps more than one. At this age, pregnancy rates remain high, with a low risk of problems and high outcomes.
At Pacific Fertility Center, in a small series of young, previously proven egg donors vitrifying eggs under age 30, we were able to achieve a 75% ongoing pregnancy rate in recipients2.
There are now five published prospective randomized controlled studies3 that demonstrate that vitrified oocytes are just as effective as fresh oocytes in producing pregnancies. While individual studies have revealed variation in egg survival and fertilization rates, it is now clear that vitrification is an excellent method to store eggs for future use, and indications are that pregnancy rates will be very close to fresh eggs.
With age, the number of eggs declines, slowly at first, then with increasing speed, until natural fertility falls to very low levels 5-10 years before menopause. Along with this decline in numbers is progressive decline in quality, with an increasing risk of chromosome abnormalities. Pregnancy rates fall with age.
We expect outcomes with fertility preservation to be related to the age of the egg as well. Age at vitrification is likely to be the best predictor of success rates. Data is currently limited, but in conventional in vitro fertilization, in patients with known fertility problems, success rates have never been better. The clinical pregnancy rate (CPR) for the first 3 quarters of 2011 in women undergoing fresh IVF and Embryo Transfer with their own eggs at Pacific Fertility Center were:
|CPR at Age||35-37||38-40||41-42||>42|
|Per Transfer (%)||36||40||34||27|
Delivered pregnancy rates will be substantially lower, but this demonstrates the improving outcomes for all age groups. Given existing studies, we anticipate that pregnancy rates per transfer after egg vitrification will be similar.
Actual data on outcomes with age is emerging. An abstract at the October ASRM meeting showed Live Birth Rate (LBR) with vitrified eggs of4:
|LBR at Age||<30||30-34||35-37||38-40||>40|
|Per Thawed Egg (%)||5.5||4.6||2.1||4.4||3.2|
|Per Transfer (%)||36||25||10||22||19|
So for women less than 30 years old, about 5% of all frozen eggs will result in a live birth, but for women >40, about 3%. Therefore, the real key to good outcomes with fertility preservation is egg numbers. The more eggs available, the better the pregnancy rates. A woman that can produce good numbers of eggs can anticipate good results with fertility preservation.
Predicting egg production is an important part of preparation for Fertility Preservation. Our recommendation is to assess oocyte numbers with clinical tests prior to fertility preservation. The parameters we use are:
- Family history
- Antral follicle count
- AMH (anti-müllerian hormone)
A woman at age 40 with a high antral follicle count and an AMH over 1.0 remains a reasonable candidate for fertility preservation.
Fertility preservation is a new field, with much to be learned and studied. We feel confident in offering the technology to women 42 and under, and expect in future studies to find the pregnancy rates to be related to the age at which the eggs were vitrified.References:
- Clinical application of oocyte vitrification: a systematic review and meta-analysis of randomized controlled trials. Ana Cobo, Ph.D, et al. Fertil Steril! 2011;96:277–85.
- AGE-BASED SUCCESS RATES AFTER ELECTIVE OOCYTE CRYOPRESERVATION (EOC): A POOLED ANALYSIS OF 2281 THAW CYCLES. A. P. Cil, K. Oktay. Institute for Fertility Preservation, Di- vision of Reproductive Medicine, Departments of Obstetrics & Gynecology and Cell Biology & Anatomy, New York Medical College, NY, NY; Obstet- rics and Gynecology, Kirikkale University School of Medicine, Kirikkale, TR, Turkey.
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