No Fertile Myrtles

By Peter Galvin, MD

Infertility affects one in six reproductive-aged couples, and declining ovarian function is a common cause of infertility in women in their late 30s to early 40s. Just like declining fertility rates worldwide, the fertility rate in the U.S. has decreased from 70.9 births per 1,000 women in 1990 to 56.1 per 1,000 women in 2022. Based on U.S. census data, age at first birth increased from 27 years in 1990 to 30 years in 2019, as more women postponed first birth. Oocytes (eggs or ova) form in the ovary from follicles. Women are born with a fixed number of follicles in their ovaries, from which oocytes are released monthly and may become fertilized to achieve pregnancy. The total number of follicles/oocytes decreases from approximately 1 to 2 million at birth to an average of 65,000 at age 25 years, 16,000 at age 35 years, and about 1,000 by menopause (approximately age 50 years). In addition, oocytes are more likely to have chromosomal defects with increasing age, leading to more miscarriages.

Few women can achieve live birth using their own oocytes after age 45 years, despite optimal diet, exercise, and use of in vitro fertilization (IVF). Rates of miscarriage are approximately 12% in women ages 20 to 29 years, 25% by age 40 years, 40% by age 43 years, and 65% in women aged 45 years and older. Age-related decline in ovarian follicles is irreversible, and currently, there are no effective methods to grow new ovarian follicles. Clinicians need to provide education about ovarian aging and decreased fertility rates associated with advancing age to couples interested in parenthood so they can make informed decisions as to when to start attempting pregnancy. Of course, other barriers to family building need to be considered, and these barriers include lack of health insurance, insufficient maternity and family leave policies at work, limited childcare options, and lack of work flexibility to accommodate pregnancy and parenthood.

IVF usually involves eight to 14 days of hormone injections, after which an oocyte is retrieved from the patient, fertilized, and then implanted into her uterus. With IVF, birth rates peak at about 40% per embryo (fertilized oocyte) in women younger than 35 years but decrease to less than 5% by age 43 years. Oocyte cryopreservation, which involves the oocyte retrieval process used in IVF, allows women to achieve pregnancy at older ages, using IVF and a frozen oocyte or embryo that was removed from her and frozen years earlier. Retrieved oocytes can be immediately frozen and fertilized when thawed or first fertilized and then frozen. There is no limit on the length of time oocytes and embryos can remain frozen. Older women who had frozen their oocytes or embryos years earlier have better rates of pregnancy and birth with IVF as opposed to older women who use their current, older oocytes or embryos, but the rates of pregnancy and live birth with frozen oocytes and embryos decline with older patient age. In the U.S., out-of-pocket costs for oocyte cryopreservation are $8,000 to $12,000 per cycle with annual storage fees of $300 to $1,000. Some employers offer insurance coverage for oocyte cryopreservation.

For more information go to the website of the National Library of Medicine at www.nlm.nih.gov

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