Banner Health Services  

Biological Clock

Dr. Moffett  

Drew V. Moffitt, MD, is a reproductive medicine specialist and division director for Reproductive Endocrinology and Infertility for the OB/GYN Residency Program at Banner – University Medical Center Phoenix. His office can be reached at (602) 343-2767.

Question:  What is my “biological clock” and when do I need to start worrying about it?

When talking about reproduction, the biological clock refers to how long a woman has until she can no longer become pregnant.

A woman is born with all of the eggs she will ever have – around two to four million in total. By the time she has her first period that number has decreased to around 400,000. More eggs are lost each month thereafter.

The most fertile eggs are the first to go. When a woman runs out of eggs, her periods stop, she is considered post-menopausal and, therefore, no longer able to reproduce. Most women go through menopause between age 45 and 55 with the average age being 51.

There is great variability when determining when a woman is “running out of eggs.” Some women are born with a lower complement of eggs, while others lose eggs at a faster pace. However, the notion of “running out of eggs” is not just about the number of eggs a woman has left. It also has to do with the quality of those remaining eggs.

It seems that the most fertile eggs are released early in life. The least fertile are lost when the “basket of eggs” gets critically low. This reality manifests as a decreased chance of having a baby as a woman ages. A woman’s chance of getting pregnant and having a baby remains constant at 20 percent until about age 34. By age 39, that chance is cut in half to only about 10 percent. 

The big question about your biological clock is, “What time is it?” Several tests have been developed to help determine if a person is running low on eggs, including a state-of-the-art lab test and ultrasound called a Biological Clock Check. These tests can give couples critical information about where they stand so that they can make informed decisions about pursuing an infertility evaluation, treatment, and what kind of treatment is right for them.

Consult a reproductive medicine specialist to help determine what your biological clock is saying.

Page Last Modified: 03/01/2015
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