Oh, wait, you're listening to Radiolab from WNYC. Hey, it's Molly. And Latif, and this is Radiolab's last episode of the year. Molly, rapid fire.
What was your favorite episode that you did not work on this year? Voice, Annie McEwan, Matt Kilty, on the mic. Those two, they should get their own show, but I don't want them to because I want them to stay here. You.
I think it had to be probably Lulu's profile of that quantum physicist Qasem in Palestine. In Palestine, yeah. And just because you feel it, you're right there with him, waiting in line for bread or whatever it is. And all he's thinking about is quantum physics.
And you're just like, what? It's just kind of a portal into a man's mind that you never would have gotten any other way. Yeah, that was amazing because, like, Lulu, you know, wasn't in Palestine, but being on the phone, it was like, there was so much sound to hear. You felt like you were there.
You felt like you were right there. Yeah, and I think the thing is, like, especially this year, how much all of these types of stories, the ones you've worked on, I've worked on, the ones we just highlighted, truly none of that would be possible without our listeners and our sustaining members. And so, thank you, thank you, thank you for, like, giving us, yeah, giving us the year we've had. I mean, because, like, it's been a hard year, right?
Right, because earlier this year, Congress eliminated all federal funding for public media, and our home station, WIC, we lost $3 million in regular, dependable annual funding. So it sort of goes with saying, I think we should definitely say that financial support from listeners is truly critical right now. And, you know, we're at the end of December, so time to support Radio Lab in 2025 is running out. So this is, like, an ask to say, please consider making a year-end donation, get us kick-started for 2026, and if you do, we have some really killer new gift options.
Yeah, just think about it like you're buying yourself a holiday gift, and the thing you get out of it is that we got a new puzzle. I love the puzzle. It's made of, like, episode art from your episode. Yeah, yeah, yeah, one of my favorites of the year, the one about the Lulucos and hot worms, but they're really bacteria.
It just, like, had this magical extremophile property where it could plug into this whole other process of read DNA, and it, like, completely revolutionized all kinds of different fields. And we've got, so we've got a puzzle, we've got a t-shirt, we've got a bumper sticker that you can, you know, put on water bottles or cars. Laptop sticker could be on anything. Laptop, exactly.
So if you want to provide ongoing support, you can join the lab, which comes with perks like sponsor-free listening, bonus content, and more, or you can make a one-time year-end donation at radiolab.org slash donate. Go to radiolab.org slash donate. And so to round out the year, you know, we look back at all our most listened to episodes, and the number one most listened to Radiolab episode of 2025, thank you for that keyboard drumroll, was our Metapause episode, which Molly hosted and which our contributing reporter Heather Radke brought the story to us. And it was so good, and we figured maybe people want to hear more.
Honestly, I think they do, because we heard back from so many people about this episode that we decided, okay, we can give you more reporting on this topic. And in fact, I did a story about the moments leading up to menopause, and this thing that my friends and I kept hearing about called the Fertility Cliff. That sounds very dramatic. Yeah, it was so dramatic that I decided, okay, I'm going to dig into this.
I want to understand what this phrase is and, like, what it actually means. And we did this story for the first time as part of a live event in 2018. And so I'm just going to play part of that live event for you here, and then we're going to have updates at the end. And here we go.
Hello, hello. How's everybody doing? All right. Well, we're so excited that you guys are here tonight.
My name is Jad. I host Radiolab and we're perfect. And I will now introduce a rising star at Radiolab and in podcasting and at WNYC and on planet Earth. Welcome, Molly Webster.
Planet Earth might have been a bit bold, I will just say. Thank you for coming. This is amazing. Hi, everyone.
Okay, so why are we all here? When I started reporting on the series, one of the first things I did was I just jumped on the phone with a lot of people. People, like, everyone in this room. I was, like, trying to hit, like, different age groups.
I wanted 18-year-olds. I wanted, like, 80-year-olds. I was calling all my friends back in the Midwest, like, hey, I haven't visited in a while, but if you could just tell me your thoughts on reproduction. Like, what's it like in the Midwest?
And then I was very, you know, I was like, oh, someone's, you know, 20 and married in Colorado? Yes, I'll call you, too. And I was basically just calling and saying, when I say the word reproduction, like, what do you do? Like, what do you think?
Are you, like, oh, God. Or, you know, interested, not interested, babies, anything more than babies? One guy talked to me about hip-hop, and I was like, I could go that way, probably won't. And there were a lot of, like, very random conversations.
And one of the things that came up in those conversations was a number. The number was 35. It took me a while to sort of notice the pattern, but I realized everyone was bringing it up in different ways. It was like, oh, I don't know, there's not that much time left.
Or, you know, women would be like, I'm drying up. My biological clock, it's ticking. There was this idea that just kept coming up over and over again. The idea that at the age of 35, your fertility vanishes if you're a woman.
It just goes up in smoke. Like, in every relationship that I'm in, I feel like it's like this countdown clock in the back of my mind. You know? And so I feel like I experience time differently.
And Bianca, the young woman on the phone here, she wasn't the only one who told us about this feeling. It came up in another conversation that we had with this woman named Chloe. She said she really, really wanted to have kids. She was in a relationship.
She and her partner got along great. Partner wasn't sure she wanted to have kids. And so on her 30th birthday, Chloe's dad sent her an email where he basically said, like, get on it. The biological clock keeps ticking, especially if you want to have several kids.
You don't want to split up with your partner because we've done nothing wrong with the biological clock. Dot, dot, dot. Thanks, Dad. It's very helpful on my birthday.
And to add flame to the fire, I talked to another woman who saw 35 at such a deadline. She decided that she was going to have a kid by herself when she was 34. She wasn't going to wait. And she told me that the doctors categorized her in a way that really surprised her.
When you're 35, you're considered a deriatric mother. It's a condition that was written on my birth chart because I was due two weeks after turning 35. And so I kept thinking as I was hearing all this stuff, I was like, I'm not freaking out about this stuff. I'm like, should I be freaking out about this stuff?
And then last October, I was on the phone with this sort of bigwig doctor in St. Louis. And the minute we got on the phone, the first thing he asked me was how old I was. I said I was 34.
And he said, you need to get on a plane and fly out here. We need to freeze those eggs. And then I thought, f*** off. And then I thought, maybe when the series is done.
And then I thought, you know, maybe I should be taking this all a little bit more seriously and actually look into this whole reproductive cliff thing. So I started reading a lot of scientific articles, watching YouTube. And I pretty quickly found what seemed to be the culprit of the cliff. So the x-axis is age.
Okay, so I need you to put on sort of your visualization cap because we're going to go through a few graphs in the story. And for this one, it is a line graph. It goes 20 to 45. And the y, the vertical line, is something called pecundability, which is the chance a couple will get pregnant after one month of trying.
And this is what the graph looked like. The shape of the graph is a line that goes pretty straight up from puberty. It stays flat until the age of 33. And then it turns and goes pretty steeply down until it hits zero.
It hears me describing it on stage as an animation of it unfolded. It goes, and then there's like a fireball at the end. So this is from a journal called Human Reproduction. It was published in 2004, and that is a cliff, if I've ever seen one.
And I think another thing that I wanted to note is that on this graph, 33 is the age where you actually should start freaking out. 35, you're already done. But there's one tiny caveat, and that is that the data behind this graph is crap. Yeah, this data is based on French peasants from the 1700s.
And you may ask, why them out of everybody? And the idea is that when they're doing fertility studies, they want, ideally, they say, populations of humans that have never used birth control. So people that are like pure from artificial hormones. And their idea was that these French peasants were the way to go.
And so this came up. It got written about a lot of different magazines, and it was the data being used to terrify women. And then so I just say, you know what, I reject this cliff since I'm done with it. And so at this point, I thought, maybe I should stop watching YouTube and actually call someone on the phone.
And so I called an epidemiologist from Boston. Her name is Lauren Wise, and she studies fertility. I know where the cliff came from. There was a very pivotal.
You do? Oh, yeah. Oh, my God. Tell me about the cliff.
So the cliff, I'm pretty sure, came from this review paper written by Brokman's. Who is this Brokman guy, and why does he get to draw a cliff on my fertility? He's a very famous reproductive endocrinologist. So after we got off the call, Lauren sent me the paper she was thinking about.
This one is a study of recent people, and it has the same axes. It's 20 to 40 is age on the bottom. And then on the side is your chance of pregnancy. And it goes...
And so this line graph, it starts high. And as it moves right, it continues just flat and unchanging. And then at some point, that line turns downward, and it arcs to the bottom of the graph, kind of like a skateboard ramp. And then it's like a little like a water slide at the end.
And I thought, well, that looks kind of like a mesa. That's like a version of a cliff. And so then I thought, well, you know, maybe this graph, I'm reacting pretty emotionally to it. So I was like, okay, this one.
And so what you see on stage is I highlight that the downward turn on the graph happens at the age of 31. 31, my friends. We should have had this event four years ago. But Lauren says, it's not really based on Greek data either.
Is it based on more peasants? No, I'm glad you asked. It is based on recent people, but it's all people that were at fertility clinics for fertility issues. So one could say it's a bit of a compromised data set.
It's not really representative of everyone. So back to where we started, begs the question, what happens if you actually look at an entire population, or like a good cross-section of the population. And Lauren, the scientist I was talking to, did actually do that. So in 2007, she launched a study with almost 3,000 Danish women who were trying to get pregnant.
We followed them forward in time for 12 months, or until they get pregnant, whichever comes first. And when you look at their data, this is what you see. So this graph looks basically like a gently sloped hill. The line starts halfway up.
It goes up, actually, a little bit more. And then it curves gently down, arcing to the bottom. Ooh, oh, oh, oh, oh, there we go. There with that.
Fertility doesn't look like a cliff at all. I feel good about that. Does anybody else? All right.
So this one, your fertility goes up for a little while. Right? 30. It goes up until you're 30.
And then when you're 35, you're actually just below the fertility you have when you're 20, which seems like, that seems great. So I thought, all right, I'm reacting very emotionally. Tell me some numbers. And so they said, for 20 to 24-year-olds, after one year of trying and having regular sex, which is actually like a technical term, so take that as you will, but I won't judge you, the chance of being pregnant, 78%.
And if you're age 35 to 40, that percentage is 72%. That feels like, oh, I'll take those odds. Yeah. So if you're in the 35 to 40-year-old age group here, as I am, that means you have a three out of four chance of getting pregnant.
And you have to keep in mind, these are rough estimates. So obviously, fertility is affected by age. It's not the only thing that's affected by age. Miscarriage rates go up as you get older.
Down syndrome rates also go up. So treat these like ballpark figures for now. But just in your mind, remember, 72% for 35 to 40-year-olds. And so to me, this graph, it's like less cliff, more like English countryside.
Like, I will go get a pint on my way to pregnancy. And this one actually made me want to call all those people we heard earlier on the phone and be like, psst, send this to your dad, right? But now I should say that our latest research from the North American study shows stronger effects. Not so fast, Webster.
Not so fast. What fertility looks like in North America, that's coming up after the break. Hi, Lulu here, and this episode is sponsored by BetterHelp. May is Mental Health Awareness Month, and as someone who reports on mental health, who likes talking to people about their mental health and what they look to in science, in the natural world, in faith, in friendship, wherever it may be, to help guide them through the rough patches of life, I just wanted to take a moment to say what seems to help people turn corners, find relief, get out of ruts, and even flourish is having someone with you.
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In the suburbs of D.C., a woman fails to show up for work and is found brutally murdered. No one was emergency. We just walked in the door and there's blood in the foyer. For the next two decades, the case remained unsolved until new technology allowed investigators to do what had once been impossible.
A new series from ABC Audio in 2020. Money, blood, and water. Listen now, wherever you get your podcasts. I'm Molly Webster.
This is Radiolab. And we are jumping right back into what a fertility cliff looks like in North America. After the Denmark study, Lauren and her team were like, well, you know, Denmark is cool, but what about other countries? So they start the same study in U.S.
and Canada. Now, this graph, as it unfolded on stage, was a real humzinger. It started high on the left and then it immediately begins to descend. It slopes down gently.
There's a bit of a bump where it regains some height and then it turns. downward this time just more steeply dropping to the bottom oh that's a tricky one expected something else um this one i i felt sadder when i looked at it i felt like this is more like this is like less english countryside more like a mountain biking championship sponsored by red bull was kind of my like my feeling on this one and this is what lauren said it is steep it's something you wouldn't want to take your kid on for a walk you would want to wear a helmet and some protective equipment and do you think the different results is different parts of the globe so like they're both truly representative of the area they're in or like that one is wrong and it's really a line and not an uphill and then a downhill oh that is such a good question molly and i don't know the answer to it it could be differences in diet and the environment and smoking it could be just all that bike riding in denmark we all just need to go to denmark honestly it seems like i should have been having sex in denmark when i was 30 exactly that is the take-home message or i should not have been and it was very good that i was in north america depending on what you want your outcome to be exactly so the danish study i think is a happier cheerier study and it's true if you look at the numbers for the north american study uh they are they are lower uh so if you're in the 37 to 39 year old age range and you have sex again regularly for one year you have a 67 chance at conception past 40 it drops to 55 so there are three things i took away from talking to lauren first it's pretty obvious that there is no cliff as another biologist i spoke with said like nothing in biology is a cliff right it's all just like a gradual change it's like a gradual decline of age and in a way there's something about it being gradual it kind of lets you choose to freak out where you want to freak out the second thing i thought about with lauren was that you know obviously it's different for everybody and these are just really big studies um and it's just averages right and the third thing was like even in the north american study at like 40 42 uh you still land at 50 percent it's not zero which to me i was like hey 50 50 that's not bad right but there was one part of the conversation that made me think about 35 in kind of a different way it started when she reminded me that there is as much as i was happy about 50 50 actually a biological deadline what is the actual end oh the average age of menopause is 50 in the united states and so maybe the thing that's going on for a lot of people is it's not so much a cliff at 35 rather 35 is an age where sort of the end comes into focus and as i was thinking more and more about the phone conversations i was having uh i realized like oh this was playing out for everybody like this is biology but the people who are like wondering about their careers and their homes and their parents like they were all sort of having the same like moment they're like oh there's something happening here where where i i feel something in front of me like in the way i never had before um it's like there's like this like little sliver of possibility before you all come back here in five years when you're 40 and we do this again so this event which was called 30 something happened live on stage in 2018 so it felt like it was time to maybe update the numbers so i called lauren back a few weeks ago and she said to me that based on sort of a larger data pool now what they're seeing is just kind of minor adjustments but if you're in the 37 to 39 year old range and you have sex regularly for one year you have a 66 chance at conception and after 40 it drops to 51 now this is unpublished data but if you look at this mapped on a graph um it doesn't really change the original shape of the graph as you heard me describe it in the episode also the term geriatric pregnancy you may now hear it as advanced maternal age and they picked 35 as a cutoff because it was linked to an evidence of decline infertility and also concern in increased risks for genetic abnormalities so it doesn't all have to do with the fertility cliff but it's often linked in conversation the other thing was that lauren looked into uh male data so i would like to hear about that yeah if you notice like in our episode we didn't we didn't dig into that but the male data it's actually it honestly surprised me it also has a shift uh downward into you know less fecundability around 35 um and it so it does decline though it does it slightly later ages than for females um one thing lauren did say is that it took 12 years to get enough data to be able to say anything about older men with any precision because there just aren't that many men in their late 40s early 50s trying to have a baby but it sounds like it's more like a it's like a fertility gentle slope as opposed to a fertility cliff yeah yeah the decline starts happening at more advanced ages and it's less of a steep slope and since we did that piece in 2018 there's all sorts of data that you know sperm does start to decrease in quality over time and so you can get more genetic abnormalities like there's greater chances of that right well you know talking about sperm makes me think of donations oh okay we're going there talking about donations makes me think of our listeners of our listeners and how grateful we are for all of them you're so grateful truly and we part of the reason we're so grateful is because we like we know what we're working on and we're really excited about it and we can't wait to get it to you i feel like if listeners smash that donate button now which is really just radiolab.org slash donate then it will help fund some of the stuff we have coming up in 2026 which for me yeah i'm hoping it's about snail sex and for you okay for me i'm working on uh brain balls brain balls yeah how new year's eve appropriate yeah yeah just picture of strike of midnight on new year's and watch the ball drop just imagine it's a brain ball yeah all right well how could you not donate to that after that after that grotesque image uh thank you thank you diane kelly for fact-checking this episode and lauren wise at boston university for all the data crunching and thank you everyone for listening for being here for 2025 yeah don't drink too much eggnog and uh have a great holiday season and we can't wait to connect with you again in the new year bye i'm valerie chin and i'm from brooklyn new york and here are the staff credits radio lab is hosted by lulu miller and let of nasser soren wheeler is our executive editor sarah sandback is our executive director our managing editor is pat walters jillan keith is our director of sound design our staff includes jeremy bloom w harry fortuna david gable maria paz gutierrez sindhu nyatna sambandum matt keelty mona magakar annie mcewen alex neeson sarah kerry anissa pizza arian whack molly webster and jessica young with help from rebecca rand our fact checkers are diane kelly emily krieger hannah pujol mazini and natalie middleton hi i'm adina i'm calling from greensburg leadership support for radio lab science programming is provided by the science foundation and the john templeton foundation foundational support for radio lab was provided by the alfred p sloan foundation every day wnyc studios is working to get closer to new york and to new yorkers the underwriting we get for businesses helps power our independence learn how your organization can join in at sponsorship.wnyc.org