UNDERSTANDING INFERTILITY
PAUSING THE BIOLOGICAL CLOCK: OOCYTE
CRYOPRESERVATION
AUTHOR Robert K. Hunter II, MD, MSc, MBA, FACOG
A
ccording to the American Society
for Reproductive Medicine, the
monthly chance of conception
for a healthy woman drops from
20% at age 30 to just 5% at age 40.
Women are born with roughly
one to two million oocytes, and
these are continuously lost over time until
menopause. While fertility technically peaks for women in their
early 20s, the reduced quantity and quality of oocytes that remain
when women reach their late 30s is the major reason that infertility
becomes more prevalent in this age group. For women seeking to
proactively protect against future infertility due to reproductive
aging or other medical causes, planned oocyte cryopreservation
(OC) is an effective option that can offer women the ability to
grow their families on a preferential timeline that is less dependent
on the inherent “biological clock.”
OC is commonly labeled as “elective” or “social” egg freezing
in the media, but notably, this technology was developed out
of necessity for a population of patients for whom fertility
preservation was anything but elective: young women with cancer.
Due to advances in oncology care, many of the malignancies
that affect young women and adolescents are now expected to
have very high long-term survival rates, often greater than 90%.
However, as these individuals grow to adulthood, many will suffer
from infertility due to the gonadotoxic effects of the chemotherapy
and/or radiation they received. Over the past 15 years, we have
seen a rapid extrapolation of the clinical and laboratory sciences
behind in vitro fertilization (IVF) into the development of a new
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LOUISVILLE MEDICINE
subfield called “oncofertility,” which is dedicated to expanding
reproductive options for cancer survivors.
For young women facing gonadotoxic therapies, several fertility
preservation options are now available for consideration. Current
American Society for Clinical Oncology guidelines recommend
that all women interested in fertility preservation be referred
for further counseling when clinically appropriate. For women
with a male partner or who are open to using donor sperm, IVF
with embryo cryopreservation is often given priority, as it will
typically yield the highest future pregnancy rates. However, for
many women, particularly those without a male partner or who
do not wish to use donor sperm, OC may be preferred. Studies
have shown that gonadotropin stimulation of the ovaries can
be started at any point in the menstrual cycle, and aromatase
inhibitors can be used to limit circulating estradiol levels in
women with hormone-sensitive malignancies. Ultrasound-guided
transvaginal oocyte aspiration procedures are typically completed
within two weeks of starting stimulation, and most women can
return to their oncologists for continued care within a few days
thereafter. A growing body of data has shown no evidence of harm
to long term outcomes for appropriately-selected candidates,
and there have been no increased risks of congenital anomalies,
chromosomal defects or cancer detected in the children that have
been subsequently conceived from these interventions.
While experiences with oncofertility provided early exposure
to OC for many reproductive medicine providers, advances
in laboratory sciences in the early 2000s helped to improve
its clinical effectiveness and encourage broader adoption into
practice. Oocytes at the metaphase II stage of meiosis have