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Fertility Cliff

December 26, 2025

AI Summary

5 min read

The Fertility Cliff That Wasn't

When Molly Webster started reporting on fertility, she kept hearing the same number from women in their twenties and thirties: 35. It came up in phone calls with friends in the Midwest, with a woman in Colorado, with a woman named Bianca who described it as "a countdown clock in the back of my mind." Another woman, Chloe, got an email from her father on her thirtieth birthday telling her to "get on it" because the biological clock keeps ticking. A third woman decided to have a child on her own at 34 rather than wait. The message was everywhere: at 35, a woman's fertility vanishes. Webster, then 34 herself, started to wonder if she should be panicking too.

The Graph That Started It All

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What you'll learn

  • 1 (01:30) **Episode Introduction** - Molly and Laithe introduce the final episode of the year, reflecting on favorite stories and thanking listeners for their support.
  • 2 (05:45) **The Fertility Cliff: A Cultural Panic** - Molly Webster begins her investigation into the widespread fear that female fertility vanishes at age 35.
  • 3 (10:36) **The Origin of the Cliff: 18th-Century French Peasants** - Molly finds the scientific graph that seems to confirm the fertility cliff, then discovers its shaky foundation.
  • 4 (12:54) **A Better Study, A Gentler Slope** - Epidemiologist Lauren Wise points Molly to a more recent study, but it too has a compromised data set.
  • 5 (15:07) **The Danish Study: A Gentle Hill** - Lauren Wise's own study of nearly 3,000 Danish women trying to conceive shows a much gentler decline.
  • 6 (17:55) **The North American Reality: A Steeper Slope** - The same study conducted in the US and Canada shows a different, steeper decline.
  • 7 (23:55) **Three Takeaways: No Cliff, Just a Slope** - Molly summarizes the key conclusions from her reporting.

+ Full timestamped outline available in the app

Show Notes

As she -- and her friends — approached the age of 35, senior correspondent Molly Webster kept hearing a phrase over and over: “fertility cliff.” It was a short-hand term to describe what she was told would happen to her fertility after she turned 35 — that is, it would drop off. Suddenly, sharply, dramatically. And this was well before she was supposed to hit menopause. Intrigued, Molly decided to look into it — what was the truth behind this so-called cliff, and when, if so, would she topple? 

This story first premiered in “Thirty Something,” a 2018 Radiolab live show that was part of, Gonads, (https://radiolab.org/series/radiolab-presents-gonads)a six-episode audio and live event series all about reproduction and the parts of us that make more of us. The live event was produced by Rachael Cusick and edited by Pat Walters.

Special thanks to epidemiologist Lauren Wise, at Boston University. Plus, Emily, Chloe, and Bianca. And of course, Jad Abumrad.

If you’re more of a visual person, here are the graphs we explain in the episode, we also include links to the corresponding papers in our Episode Citations Section, below!

LINK TO GRAPHS:
https://media.wnyc.org/i/1860/1046/c/80/2025/12/FERTILITY_AGE_GRAPHS_1-4.jpg

EPISODE CREDITS: 
Reported by - Molly Webster
Produced by - Arianne Wack
Fact-checking by - Diane A. Kelly

EPISODE CITATIONS:

Audio:

Videos:

“Radiolab Presents: Thirty Something”
https://youtu.be/LOJVAaSwags?si=czCBraHf1JEqmAQi

Research Articles:

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