Let’s talk about the idea of a "biological clock" and its impact on fertility and our well-being

Reviewed by Health Guide Team, 

Written by Jordyn Rozensky 

Reviewed by Health Guide Team, 

Written by Jordyn Rozensky 

last updated: Feb 25, 2020

6 min read

Whether or not you know you want to have children, you’re probably familiar with the notion of a “biological clock.” The concept that people with uteruses have a limited amount of time to get pregnant is a linchpin of conversations about women. We see it demonstrated by the recent creepy tweet pondering Taylor Swift's fertility and our ongoing obsession with Jennifer Aniston's childfree life.

The concept of a ticking biological fertility clock is a somewhat modern one. The Washington Post first used the phrase “the biological clock” in an article in 1978 called “The Clock Is Ticking for the Career Woman.” The author, Richard Cohen, declared: “Most [women] said that they could hear the clock ticking… … You hear it wherever you go.”

Ann Kirchheimer, a writer for the Boston Globe, followed Cohen soon after, reporting that “the beneficiaries of the women’s movement, a first generation of liberated young ladies … who opted for careers, travel, independence rather than husband, home, and baby are older now and suddenly the ticking of the biological clock is getting louder and louder.”

In Belle Bogg’s memoir, The Art of Waiting: Fertility, Medicine, and Motherhood, Finnish sociologist Anna Rotkirch calls the idea of the biological clock “an emotion which may be typical for societies when women have many choices.”

These news stories have added to the pressure that many women feel, with fears of running out of time influencing reproductive decisions. To help with the external and internal pressures of your biological clock, we’re breaking the concepts down for you — and examining how information about your body can help you feel in control.

Modern Fertility

Fertility hormones shouldn’t be a mystery

First things first: What exactly is a biological clock?

Your biological clock is indeed a real thing — it isn’t only a metaphor related to fertility. Your body has natural rhythms and regulates day-to-day functions, from metabolism to sleep cycles. Instead of cogs and metal, our biological clocks are made up of proteins that send messages to the entire body. And it isn’t just us humans that have biological regulation. Similar mechanisms can be found in fruit flies and mice, to name a few examples.

Alice Walton explores the idea of the natural rhythms of our clock in The Atlantic, writing, “Research has been finding that the body's clock is responsible for more than just sleep and wakefulness. Other systems, like hunger, mental alertness, and mood, stress, heart function, and immunity also operate on a daily rhythm.”

The clock doesn’t “stop” at age 35

The biological cloc is most commonly referred to as a timeline for having children. There are some myths floating around saying that 35 years old is a fertility “cutoff.” But, unfortunately, a lot of how society looks at age and fertility is outdated.

A 2013 article in The Atlantic found that much of the information we’ve been relying upon for fertility data is from French birth records from 1670 to 1830. (Imagine seeing a doctor today whose treatment plans, tools, and knowledge hadn’t grown or shifted in the past 200 years!) The article explains:

“The widely cited statistic that one in three women ages 35 to 39 will not be pregnant after a year of trying, for instance, is based on an article published in 2004 in the journal Human Reproduction. Rarely mentioned is the source of the data: French birth records from 1670 to 1830.”

Needless to say, life in 2020 is different than life in the 1670s, yet these myths that the cutoff for fertility is 35 remain prevalent.

Rachel, a mother of two, lost a pregnancy recently. When speaking with a doctor, she inquired about when and if she could try again, and was told that at 35 pregnancy was impossible, as if the biological clock was a literal clock that froze at an exact age. Says Rachel, “I felt mostly amused because there really is very little different about a pregnancy at 34.5 than at 35. It's not an extremely steep rise in risks, right at the moment of my birthday, you know? I got a new doctor immediately.”

Unfortunately, while it’s a misconception that the clock “stops” at age 35, it is a biological reality that waiting to have kids later in life may make it more difficult to have kids. As you get older, there's actually a gradual fertility decline. Why is that? Because, at birth, we’re born with all of our eggs, and once we start ovulating, our ovarian reserve (or the number of eggs we have) decreases over time. The quality of our eggs also diminishes.

While a reduced ovarian reserve is a biological reality, you can keep track of your unique fertility curve by testing your anti-Mullerian hormone levels (AMH). AMH is the best predictor we have for ovarian reserve because it’s produced by cells in our developing ovarian follicles — meaning AMH levels indicate the number of eggs available for ovulation.

Can you “pause” your biological clock?

Many people refer to new fertility technologies like egg freezing as a way to “pause” our biological clocks — but the jury’s still out on how true that is.

The reason egg freezing can make getting pregnant when you’re older easier is that it allows you to preserve some of the quality and quantity of your eggs from a younger age.

But it’s important to remember that egg freezing isn’t a guarantee — successful implantation is totally dependent on how our bodies respond to in-vitro fertilization (IVF).

Age isn’t the only factor that affects fertility

Your age isn’t the only thing that can impact your ability to conceive and carry a healthy pregnancy to term. Your genes and lifestyle can also play a role:

  • Genetic predispositions: Early onset of menopause and certain conditions that impact fertility can run in your family. (All the more reason to talk with your relatives about your plans for kids!)

  • Body-fat percentage: High or low percentages can throw off your hormones and impact ovulation.

  • Smoking: The use of both cigarettes and vapes are linked to fertility issues.

  • Stress levels: Many of our body systems, including reproductive, can shut down in response to high levels of stress.

Bottom line? Your fertility is much more than just the number of years you’ve lived.

Not everyone feels the tick tocks of a biological clock

Diana has never felt the urge to have children. In fact, the very idea of a ticking clock is one she finds insulting; for Diana, and many others, a biological need for children implies that a woman’s only role is to have children. “I’ve always talked about wanting dogs, not kids,” she says.

Still, she has felt external pressure around her decisions. Diana has experienced people (and even potential partners) asking her if and when she wants to have kids — and why she hasn’t had any. “I tell them that’s not my only purpose in life. Plus, I enjoy living life childfree. I have the freedom to be fabulous,” she explains.

Des feels similarly. She’s never heard a ticking clock telling her body it’s time. “As a lesbian in my late 30s, people often assume that when I say ‘I don’t want children,’ it actually means ‘I want children but I cannot have them “naturally.” Many people feel compelled to say that ’I still have time.’ I typically just smile and change the topic, but inside I’m like... ‘really?’ I know people are trying to be nice, but somehow I can’t believe that … it is still assumed that every woman wants children.”

Des and Diana were two of many individuals we heard from who simply have never felt a biological need to have children. If you’re not feeling an internal pressure to have children, either because your “biological clock” isn’t speaking to you or because you’re focused on other areas in your life, you're not alone.

But if you do feel pressure to have a baby by a certain age...

Experiencing the pressure of a “biological clock” and worrying that you’re running out of time is a very real feeling — and if this is something you’re dealing with, it’s important to stop and reflect on all of the factors at play.

According to an article in Psychology Today, people should “be cautious about metaphors like the ‘biological clock’ — don’t take them literally. The popularity of this metaphor is still strong, and it still supports a traditional view of women.” The article’s author, Catherine Aponte, reminds the reader that many women have babies in their 40s — and that focusing on time constraints of a biological clock can be more harmful than good, forcing you into parenthood before you’re ready.

For Sara Beth, an educator in NYC who has written publicly about her relationship and desire to start a family, the question of running out of time was a big one and was the root of anxiety. When she became a widow, she began to wonder if her chance at having children had passed as well. “I worried that my physical plant was already shutting down, and it felt like growing my own baby might not be in the cards for me,” she wrote. “There are many ways to start a family, of course, but I was thinking about how my insides were functioning. Constantly.”

Sara Beth struggled with these concepts for a long time, but after she recently married, they almost immediately discovered she was pregnant. It was a good reminder for Sara Beth that so much of fertility is out of our hands — and stressing over it won’t change that. “I’ve struggled in my way, and waited longer than I ever thought I’d have to, and [learned] that nobody has complete control over their own timeline, as much as us planners would like to hope.”

If you’re feeling pressure to conceive, be sure to make decisions based on your own life and your own body — not others’ expectations. Find someone to talk to and actively seek more information about your own fertility. The more information you have about your own health and fertility, the less you leave up to chance.

When you’re planning your future, information is your friend

If you’re wondering about your timeline and your future fertility, the best thing you can do is arm yourself with knowledge. Understanding your hormone levels can give you a better sense of your fertility timeline, if egg freezing is a good option for you, potential in-vitro fertilization (IVF) outcomes, and even menopause onset.

If you’re feeling pressure to have children, remember that age, biology, and lifestyle all play a role in fertility. Information can make a difference in calming down the tick tocks of that biological clock.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

February 25, 2020

Written by

Jordyn Rozensky

Fact checked by

Health Guide Team

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