WS MoreOrLess: Fertility - when is too late?

Summary

More or Less: "Fertility - when is too late?"

BBC Radio 4, World Service — October 26, 2013
Host: Tim Harford
Contributors: Hannah Barnes, Jean Twenge, David James, Robert Winston

---

Episode Overview

In this episode, Tim Harford and the More or Less team delve into the numbers and myths surrounding age and female fertility. Inspired by panic-inducing media headlines and anecdotal fears, the show challenges widespread claims about the precipitous decline in fertility after age 35. Through interviews with researchers and fertility experts, the episode separates outdated statistics from up-to-date evidence, offering a more nuanced look at conception chances for women (and men) as they age.

---

Key Discussion Points & Insights

1. Media Myths and Outdated Statistics [00:18–02:13]

• Tim highlights the recurring media narrative that presses women to have babies before 35, referencing comedic takes and alarming magazine headlines.

• Jean Twenge, psychology professor, recounts her own fears after reading that “one out of three women over the age of 35 will not be able to get pregnant within a year.”

  • Quote (Jean Twenge, 01:32):
    “One out of three women over the age of 35 will not be able to get pregnant within a year.”

• Investigation reveals this statistic is based on 18th-century French birth records—women with vastly different life circumstances (poor health, no modern medicine, and no birth control).

  • Quote (Jean Twenge, 01:48):
    “The data on which that statistic is based is from birth records from 1700s France.”
  • Quote (Tim Harford, 02:02):
    “We’re talking about women who, you know, have never seen electric light bulb, no antibiotics, no modern health care.”

2. Modern Data Paints a More Optimistic Picture [02:13–03:49]

• Jean Twenge and Tim point to more recent, relevant research: the 2004 David Dunson study.
• Findings from this contemporary study:
  • 82% of women aged 35–39 conceive within a year—very close to the success rate (86%) for women in their late 20s and early 30s.
  • Only about 1 in 5 women over 35 will not conceive in a year, not 1 in 3 as often claimed.
• Many women who have difficulty conceiving at 35+ would likely have struggled at younger ages as well.
• Quote (Tim Harford, 03:01):
  “Instead of one in three women in their late 30s not being pregnant after a year of trying, this study said that fewer than one in five women would be in that position.”

3. Expert Perspective: How Reliable Are the Numbers? [03:49–04:44]

• David James (NICE) confirms the Dunson study is more reliable for today’s women than historic data.
  • Historic studies often didn’t consider women actively trying to conceive or potential use of rudimentary birth control.
  • Quote (David James, 04:12):
    “This was a report which should not have been used to form the basis of saying what is the chance of a woman conceiving at age whatever.”
• He also notes that statistics based on IVF or artificial insemination can be misleading, as participants already have identified fertility problems.

4. What About Fertility at 40 and Beyond? [05:10–05:49]

• Limited, low-quality data, but it’s clear chances decline after 40, though it’s “certainly not impossible” to conceive.
• Notable celebrity pregnancies “in early or indeed late 40s” show it can happen, but chances drop compared to the late 30s.

5. Is Fertility Increasing Over Time? [05:49–06:15]

• David James notes that women’s natural conception chances at age 40 are higher now than when previous medical guidelines were written.
• Improvements attributed to better health, medical advances, and lifestyle factors.

6. A Positive Spin: Social Benefits [06:15–06:44]

• Lord Robert Winston, eminent fertility expert, praises the trend of later motherhood—citing greater stability, better health, and social advantages—though he acknowledges some “payoff” in fertility risk.
  • Quote (Robert Winston, 06:28):
    “I think it’s great that women are having babies later and later in life... But of course, there is some degree of payoff in fertility problems, and that is a risk, but it’s not a major risk.”

7. Other Age-Related Risks [06:44–07:49]

• Risks such as chromosomal abnormalities (e.g., Down syndrome) and miscarriage do increase with age, as does the likelihood of pregnancy complications like high blood pressure.
  • Example: At 40, the risk of a chromosomal abnormality is about 1 in 60.
  • Quote (David James, 07:06):
    “The risk of any chromosomal abnormality at the age of 20 is 1 in 500. At the age of 30, it’s about 1 in 400. At the age of 40, it’s about 1 in 60 to 70... 59 out of 60 women age 40 will have no chromosomal problem in their baby at all. One has to keep a sense of perspective.”
• Most women over 35 and even 40 who conceive will have a normal pregnancy and outcome.

8. Male Fertility and Age [07:49–08:24]

• Less data on men, but the Dunson study indicates male fertility also declines after the late 30s.
• If a woman aged 35’s partner is 40, the chance of conceiving in a year drops to 72% from 82%.

9. Practical Advice and Lighter Moments [08:24–08:46]

• Any tips for conception? Lord Robert Winston recommends a classic approach:
  • Quote (Robert Winston, 08:32):
    “The best way to have a baby is either in bed or on the...by the far side, on the hearthrug or whatever.”

---

Notable Quotes

• Jean Twenge [01:32]:
  “One out of three women over the age of 35 will not be able to get pregnant within a year.”
• Tim Harford [03:01]:
  “Instead of one in three women in their late 30s not being pregnant after a year of trying, this study said that fewer than one in five women would be in that position.”
• David James [07:06]:
  “...59 out of 60 women age 40 will have no chromosomal problem in their baby at all. One has to keep a sense of perspective.”
• Robert Winston [06:28]:
  “I think it’s great that women are having babies later and later in life.”

---

Timestamps for Key Segments

| Segment | Timestamps | |---------------------------------------------|--------------| | Introduction & media myths | 00:18–01:37 | | Historic vs. modern statistics | 01:37–03:24 | | Expert takes on best data sources | 03:24–04:44 | | Odds of pregnancy at 40+ | 05:10–05:49 | | Birth trends and health improvements | 05:49–06:15 | | Social advantages of later motherhood | 06:15–06:44 | | Age-related risks (chromosomal, miscarriage)| 06:44–07:49 | | Male fertility and age | 07:49–08:24 | | Practical advice (humor) | 08:24–08:46 |

---

Conclusion

More or Less takes a characteristically rigorous and reassuring look at fertility statistics and age, debunking alarmist myths with contemporary data and expert insight. While fertility and risks do decline and rise with age, they do not follow the steep drop-offs so often cited in headlines. The main message: For most couples, trying to conceive in their late 30s—and even their early 40s—realistically offers better odds, and lower risks, than sensationalist statistics suggest.

Host’s closing wish:
"For those of you who are currently trying for a baby, good luck, have fun..." [08:46]

Transcript

[Hannah Barnes]

This is the short edition of More or Less, first broadcast on the BBC World Service.

[BBC Announcer]

Thank you for downloading from the BBC. For details of our complete range of podcasts and our terms of use, go to bbcworldservice.com podcasts

[Tim Harford]

hello, and welcome to More or Less on the BBC World Service, the program which smites the dragon of dodgy data with a shining sword of statistical straight talking. I'm Tim Harford. The comedian Tina Fey has been looking at her magazine collection.

[Saturday Night Live Comedian]

The COVID story of New York magazine this week is Baby Panic. This goes perfectly with the other magazines on my coffee table. Where are the babies? Why haven't you had a baby? And for God's sake, have a baby?

[Tim Harford]

That's from the US show Saturday Night Live back in 2002. It is, of course, possible that some of those headlines weren't genuine, but this one is. Have babies by age 35, say experts, and so is this one.

[Hannah Barnes]

Pregnancy after 35 is like an Ironman challenge.

[Tim Harford]

Let me tell you the story of Jean Twenge, a professor of psychology at San Diego University. Back when that edition of Saturday Night Live went out, Jean was having a tough time. She was 30 years old and on the verge of a divorce. A few years later, she had found love again. Hurrah. But Jean and her new husband wanted to have children, and panic quickly set in.

[Jean Twenge]

I read a lot of very scary

[Tim Harford]

statistics, and one in particular made her feel pretty desperate.

[Jean Twenge]

One out of three women over the age of 35 will not be able to get pregnant within a year.

[Tim Harford]

So that means that after 12 months of trying to conceive naturally, only 2/3 of women will have been successful. But Jean was determined to find out more. Where had that figure come from?

[Jean Twenge]

The data on which that statistic is based is from birth records from 1700s France.

[Tim Harford]

1700s France, yeah, yeah.

[Jean Twenge]

I mean, 1680 to 1810 or something like that.

[Tim Harford]

We're talking about women who, you know, have never seen electric light bulb, no antibiotics, no modern health care. I mean, it's quite extraordinary that that's where the data is coming from.

[Jean Twenge]

Well, you know, I can I empathize slightly with the researchers in this area because it is difficult to draw conclusions about age and fertility from modern populations where birth control is widely used.

[Tim Harford]

But surely there are some more modern studies. In her statistical search, Jean then came across a paper by David Dunson at Duke University in the U.S. it was

[Jean Twenge]

published in 2004, and it found that women over 35 had a much higher chance of getting pregnant than those historic birth records would suggest it found 82% got pregnant within a year. What was really interesting is that wasn't all that different from women in their late 20s and early 30s where the figure was 86%.

[Tim Harford]

So to put that another way, instead of one in three women in their late 30s not being pregnant after a year of trying, this study said that fewer than one in five women would be in that position. And of the women who did have trouble conceiving, many of them would have had trouble even if. If they'd started trying earlier on. Now, our reporter Hannah Barnes is with me now. And Hannah Jean was looking at data and statistics widely quoted in the United States.

[Hannah Barnes]

Yeah, and similar stats are quoted elsewhere too. The question is, do the experts back her up? And they do. I've been talking to David James from the National Institute for Health and Care Excellence in the uk. He said the Dunson study was far more reliable than studies which use historic data, and that the Dunson numbers are the ones which modern trying to conceive should be looking at.

[David James]

It was a single study undertaken relatively recently of about 780 women in seven different European centres. And the important point about that was that these were women who were trying to conceive. The other study which produced these very pessimistic figures for chances of success were actually merely reporting the reproductive performance in a group of, of women over many centuries without the same criteria of intending to get pregnancy. So in other words, this was a report which should not have been used to form the basis of saying what is the chance of a woman conceiving at age whatever.

[Hannah Barnes]

And of course, they could have actively been trying to avoid getting pregnant.

[David James]

Correct. They may not have had intercourse. I mean, that's rather crucial to the chance of success, too.

[Hannah Barnes]

Alongside the studies that look at women hundreds of years ago, we're also often confronted with statistics looking at IVF success rates or artificial insemination. And there are obvious problems with both of those. Couples undergoing ivf, for example, have an established fertility problem. They've already tried and failed to conceive naturally. And with artificial insemination, the numbers show that the success rates just aren't as high as natural conception rates.

[Tim Harford]

Okay, so back to couples trying to conceive naturally. We've been talking about the chances of women getting pregnant in their late 30s. What happens at 40?

[Hannah Barnes]

Well, there hasn't actually been very much research on it, but David James, who helped compile the NICE guideline on fertility, says 40 isn't an absolute cutoff point,

[David James]

it would appear from the limited and poor quality data that we have that that rate falls significantly. But as we know, for some notable celebrity cases, it is not impossible to get pregn in early or indeed late 40s. But the chances are certainly much less than they are when a woman is in her late 30s.

[Hannah Barnes]

Is there any evidence that generally fertility is just increasing as time goes on?

[David James]

Yes, is the short answer. And we've recently updated the NICE guideline on fertility, and it is clear that the chances of women naturally conceiving at the age of 40 are much higher now than they were when the original guideline was written.

[Hannah Barnes]

I've also been talking about this to another fertility expert, Robert Winston, a man so eminent he is emeritus professor of Fertility Studies at Imperial College London and was made a lord by Queen Elizabeth ii.

[Robert Winston]

I think it's great that women are having babies later and later in life. I mean, there are all sorts of advantages nowadays. Our health is better, they're more secure, they're often in a stable relationship. But of course, there is some degree of payoff in fertility problems, and that is a risk, but it's not a major risk.

[Tim Harford]

But of course, there are other risks with delaying having children, the chance of having a baby with chromosomal abnormalities, the most common of which is down syndrome. That chance also increases.

[Hannah Barnes]

It does, and so does miscarriage. And Jean Twenge accepts all of that in her book the Impatient Woman's Guide to Getting Pregnant. But again, it might be that those risks are overstated. Here's David James.

[David James]

The risk of any chromosomal abnormality at the age of 20 is 1 in 500. At the age of 30, it's about 1 in 400. At the age of 40, it's about 1 in 60 to 70. Turning that on its head, if you take the 1 in 60 figure for age 40 women, it does mean that 59 out of 60 women age 40 will have no chromosomal problem in their baby at all. One has to keep a sense of perspective. If you're 40, you have twice the chance of having blood pressure problems in pregnancy than if you're 30. But the figure are 2%, rising to 4%. In other words, the great majority of women who conceive and carry their babies in their late 30s, and indeed, if you're 40, will have a normal outcome to their pregnancy.

[Tim Harford]

Hannah, lots of talk about women. What do we know about male fertility and how that changes with age?

[Hannah Barnes]

Well, there's nowhere near as much data on it, but the David Dunson study we've been talking about does look at it. He concludes that the impact of age on male fertility becomes pronounced from around the late 30s. Now, that study presumes that partners the same age. So if we take that statistic, 82% of women aged 35 will conceive within a year of trying. That falls a full 10 percentage points to 72% if the male partner is 40, just five years older.

[Tim Harford]

Now, just finally, did you pick up any handy tips for couples trying to have a baby?

[Hannah Barnes]

Funny you should say that. Robert Winston did have a suggestion.

[Robert Winston]

The fact of the matter is that the best way to have a baby is either in bed or on the, you know, by the far side, on the hearthrug or whatever.

[Tim Harford]

And that's all we have time for this week. If there's a number you'd like us to investigate, you can email us at more or lessbc.co.uk and you can listen to more editions of the program and sign up for a free download at our website, bbcworldservice.com moreorless and for those of you who are currently trying for a baby, good luck, have fun, and until next week, goodbye.

[BBC Announcer]

There are dozens of different podcasts now available from the BBC, including news, documentaries, science, business, arts and sports. For details of them all, go to bbcworldservice.com podcasts.