Fertility Blog

Fertility Preservation and Family Building

Building a family on your own terms, having children when you want and with whom you want, is empowered by Fertility Preservation.

The egg has immense power to change lives. An embryo, a fertilized egg, is the first step to pregnancy and family building, the origin of the connection of mother to child, and the link between future and prior generations. A new child is a connection to the world, to our schools and to our communities, and a core of the fabric of our society.

The egg is the only human cell that can accept DNA from another human being, a male, and has the incredible and unique capability of combining the DNA of two individuals into a new embryo with the potential for pregnancy. The egg is a powerful structure, managing early cell division and maintaining the right balance of chromosomes for the developing embryo.

Eggs are a limited and valuable resource. From the start, egg numbers decline through the first 50 years of life. All the eggs for a lifetime are produced prior to delivery of a baby, then there is a progressive and irreversible loss of those eggs. At age 13, 2/3 of the eggs are gone, and 90% by age 30, and virtually 100% at menopause, around age 51 in the US.

Eggs age and decline in quality, along with cells in the rest of the body. Managing chromosomes is a difficult process at any age that becomes more difficult with age. In older age groups, producing a chromosomally normal embryo can become quite challenging. In a young woman, a 25 year-old, about 1/3 of her eggs manage the chromosomes appropriately and produce a chromosomally normal (euploid) embryo. The yield of euploid embryos declines to 10% at age 35 and 3-5% of eggs by age 40.

So with age, a woman will find fewer and fewer eggs and those fewer eggs are lower quality, with higher risk of aneuploidy. An older woman will experience more challenges conceiving, with a lower pregnancy rate, more miscarriages and rising risk for chromosomal aneuploidies and genetic illness in children, for instance Down Syndrome.

In October 2012 The American Society for Reproductive Medicine (ASRM) published practice guidelines that removed the experimental label from oocyte cryopreservation. To date, there have been over 2,500 live births achieved from oocyte cryopreservation without an increase in pregnancy complications or congenital anomalies.

Ovarian reserve testing provides some guidance. Ultrasound and a blood test for AMH are useful tools to assess egg counts. Every month, out of the thousands of microscopic eggs in the ovary, a few bubble up to produce antral follicles. Antral follicles can be seen on ultrasound of the ovaries. The antral follicles produce AMH (anti-Mullerian Hormone). Measurement of AMH correlates to egg numbers and predicts the response to stimulation.

Egg quality and the presence of chromosomal errors is more challenging to predict. The changes are subtle, and there are no blood tests or imaging studies that reflect these changes. The best predictors of egg quality and normal chromosomes are age and family history. There clearly is a correlation between mothers that conceive easily, especially at later ages, and their daughters.

Egg freezing was originally performed using a slow free technology, now we use vitrification. Vitrification is a freezing method that encases a cell in a glass-like bubble. Vitrification does not cause ice crystal formation and therefore causes less damage to cells. We see survival rates and fertilization rates of those eggs at 80-85%.

Pregnancy rates with eggs vary by age, from around 20% per egg to 1-3 % in older age groups. While data is limited, we have pregnancy success with a 41 year old frozen egg. This means that to give a good chance of a single pregnancy 5-10 eggs are required. Older age groups may require 20-50. Pregnancy outcomes are never guaranteed. While fertility preservation provides a risk reduction strategy from the certain loss of future fertility to some chance of success at a later time, some women will not be successful with the technique. This risk rises with age.

Embryo cryopreservation is an excellent alternative to egg freezing, when considering the outcome of successful pregnancy. A chromosomally normal embryo will produce pregnancy rates of 50-70%, about 5 times higher than a cryopreserved egg. Embryos of course require sperm, since the egg is fertilized. The option to decide sperm in the future is lost when freezing embryos.

Data looking at children created from egg vitrification has been reassuring. There has not been an increase in aneuploidy or birth defects from these children. We hope to establish a national data collection effort to study these pregnancies in more detail. The literature has demonstrated comparable pregnancy rates between fresh and frozen oocytes. Cobo and Diaz published data from the use of 22741 frozen oocytes. Pregnancy rates in the vitrified oocyte group were 49.1% compared to 48.3% in the fresh group.

We have vitrified over 20,000 oocytes and have hundreds of pregnancies from these eggs, one of the largest experiences in the United States.
 
Suggested readings:
Steiner et al. Associations between biomarkers of ovarian reserve and infertility among older women of reproductive age. JAMA. 2017:318(14):1367-76.
Goldman et al. Predicting the likelihood of live birth for elective oocyte cryopreservation: a counseling tool for physicians and patients Hum Reprod 2017 32(4): 853-859

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