3 Things to Know About Your ‘Biological Clock’

The concept of a ticking fertility clock is a somewhat modern one, but it’s pretty pervasive in our society. So, let’s talk about the idea of a biological clock. 

The concept revolves around the fact that people with uteruses have a limited amount of time to get pregnant. Because of this, many of the cautions about running out of time are aimed at career women, who put off starting a family to focus on their careers. These types of conversations add pressure to how women feel about their fertility and decisions about their own bodies.  

At Arizona Center for Reproductive Endocrinology & Infertility, we want to help clear up any misconceptions and perhaps alleviate some of the pressures of your biological clock. Here’s what you should know about its true impact on fertility.  

The biological clock is a real thing. 

Unfortunately, the biological clock isn’t a made-up concept or metaphor; it is indeed a real thing. It’s actually located in the hypothalamus, a part of the brain that controls basic biological activity. Your natural circadian rhythms send messages to the body and regulate day-to-day functions, like your metabolism and sleep cycle. These rhythms, or your ‘clock,’ are also responsible for other systems, like hunger, mood, stress, alertness, respiratory rate, heart rate, immunity, and fertility. Interestingly, it isn’t just humans that have a biological clock—birds, mammals, and reptiles have them as well.  

But it doesn’t stop ticking at a specific age. 

When referring to the biological clock in terms of fertility, which is typically the most common usage, there’s the idea that it stops ticking around age 35. Meaning, the fertility cutoff for people with uteruses is 35 years old. Again, the biological clock controls so much more than reproduction, so it won’t ever just stop. However, when people with uteruses do reach their mid-30s, it does become more difficult to conceive naturally. In fact, by age 40, only around 1 in 10 women will get pregnant per menstrual cycle.  

This is because, as you get older, there is a gradual fertility declineAt birth, people with uteruses are born with all of their eggs, and once they start ovulating, their ovarian reserve (or the number of eggs they have) decreases over time, so does the quality of those eggs. Yet, despite the challenges, many women older than 35 years can still have successful pregnancies and healthy babies. 

You can ‘pause’ your fertility clock. 

Often, fertility technologies—like egg freezing—are considered to be a way to pause your biological clocks. The procedure can make getting pregnant at an older age easier, because it preserves healthier, more viable eggs from a younger age. Of course, this requires some prior planning, but if you feel like you’re hearing the ticking of your biological clock, freezing your eggs now can reduce some of that stress or pressure—allowing you to get pregnant at a later date. Egg freezing is like an insurance policy, but it’s not a guarantee; every woman’s chances of successful implantation and pregnancy are different. 


Remember, age, biology, and lifestyle all play a role in fertility—it doesn’t just come down to your ‘biological clock.’ However, if you are currently experiencing the pressure of a ticking clock and concerned that you’re running out of time to start your family, we encourage you to contact AZCREI. We’ll be able to give you a more accurate picture of your fertility and help you plan your next right steps in regards to ‘pausing’ your clock or getting pregnant sooner. To schedule a consultation with Dr. Gelety and our AZCREI team, give us a call at (520) 326-0001 or visit us online. 

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