Terminology Tuesdays: “Tick-Tock, Tick-Tock…”

For Terminology Tuesdays this week, I would like to discuss age-related decline in fertility.

We have all heard about the “biological clock.” The ticking of that clock ticks louder for many women as they get closer and closer to the end of their fertility. Women are born with all the eggs (oocytes) they will have in a lifetime. As a woman ages, the number of eggs in the ovaries declines naturally and progressively. Once these eggs are gone, menopause ensues. So, hearing the ticking of that biological clock is understandable as a woman ages.

While in utero, a female fetus will have developed 6-7 million eggs by the 20^th week of gestation. The Committee on Gynecologic Practice of the American College of Obstetricians and Gynecologists and the Practice Committee of the American Society for Reproductive Medicine state, “The number of oocytes decreases to approximately 1–2 million oocytes at birth, 300,000–500,000 at puberty, 25,000 at age 37 years, and 1,000 at age 51 years, the average age of menopause in the United States.”

Age has a significant impact on female fertility. The Committees state that the ability to achieve a live birth “declines gradually but significantly beginning approximately at age 32 years, and decreases more rapidly after age 37 years, reflecting primarily a decrease in egg quality.” The Committees also state that this decline in fertility can also be attributed to the fact that as a woman ages, she has a higher chance of other disorders (such as fibroids, tubal disease, and endometriosis) adversely affecting her fertility.

This decline in fertility can be demonstrated in success rates from IVF. The Committees state, “For the year 2006, the percentage of embryo transfers resulting in live births decreased progressively from 44.9% in women younger than 35 years to 37.3% for women aged 35–37 years, 26.6% for women aged 38–40 years, 15.2% for women aged 41–42 years, and 6.7% for women aged 43–44 years.”

Additionally, with increasing age, there is an associated increased risk for pregnancies with abnormal chromosomes and pregnancies leading to miscarriage. The Committees summarize by saying, “Therefore, given the anticipated age-related decline in fertility, the increased incidence of disorders that impair fertility, and the higher risk of pregnancy loss, women older than 35 years should receive expedited evaluation and treatment after 6 months of failed attempts to conceive, or earlier if clinically indicated.”

If you hear your “biological clock” ticking louder, contact your local fertility clinic. A great place to start looking for a fertility doctor is at the Attain IVF website.

Source: Fertility and Sterility, Volume 90, Issue 5, Page S154-5, November 2008, Authors: The Committee on Gynecologic Practice of the American College of Obstetricians and Gynecologists and The Practice Committee of the American Society for Reproductive Medicine.

Dr. Lowell T. Ku, M.D. is a leading Reproductive Endocrinology and Infertility specialist at Dallas IVF, one the nation’s premiere infertility centers.  Dr. Ku clarifies the many confusing terms used in the world of Infertility using straightforward explanations.