Six myths about having children
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Men don't have a biological clock
In reality, men face a decline in sperm count and quality as they age. Older men are also more likely to have children with disorders. The research is mixed on how soon this becomes a noticeable problem, but one thing is clear: male biological fertility declines markedly over time too.
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Men can just delay parenthood and marry a younger woman
The average age gap in heterosexual married couples is 2–3 years in the UK, with gaps of over 10 years being very uncommon. Guys can’t just rely on marrying a younger woman to have kids.
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Women can wait risk-free to 30+ to have family
To have a 90% chance of having 3 children without IVF, a woman needs to start trying for children at 23 years old. With IVF, the age raises to 27.
During the 30s, it continues to get more difficult for women—the risk of being in an infertile couples rises by 36% for women between the age of 30 and 35. Most 40 year old women trying for children are in infertile couples.
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You can just use IVF in your late 30s/early 40s
IVF success rates are around 1 in 6 for women aged 40–42. It’s still less than 1 in 10 for women aged 43–44.
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Children are terrible for carbon emissions
The study that found this used outdated emissions data from when Western world emissions were at their highest. Once the downward trend in emissions is taken into account, even if Western fertility was restored to replacement level, it would only add 0.05 degrees celsius in warming by 2200.
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We can't feed more people
Various models and papers have found that we can sustainably feed more than 10 billion people and global population is not currently forecast to exceed that level.
Are children bad for the planet? The maths says no
A once-viral statistic has scared a generation into smaller families. Newer research tells a very different story.
IN SHORT
- The claim that having a child is the worst thing you can do for the climate rests on outdated 2005 emissions data.
- A 2023 paper using up-to-date trends found restoring replacement fertility would raise warming by just 0.05°C — by 2200.
- Parents tend to have lower personal emissions than non-parents at the same income level.
- A larger population can mean cheaper shared infrastructure and more people working on the problem.
"The single most important thing you can do to fight climate change is not have children." It's the kind of claim that's been repeated in geography classrooms, opinion columns and viral posts for almost a decade — often persuasively enough that people who want children decide against it.
1why it stuck
Surveys suggest a meaningful share of people cite environmental worry as a reason to have fewer children, or none. Even on a conservative reading — assuming only one in ten of those responses reflects a genuine, decisive reason rather than a convenient one — that's still roughly 1 in 100 people. In the UK alone, that could mean 700,000 people, over the course of their lives, choosing not to become parents because of a claim that doesn't hold up to scrutiny.
2what the evidence actually shows
- Old data, worse assumptions. The famous 2017 study behind the claim borrowed its numbers from 2009 research built on 2005 emissions data — close to the historical peak for per-person emissions in the developed world.
- Double-counting the future. That 2009 estimate also tacked on a "carbon legacy" for hypothetical grandchildren, projected using fertility and emissions trends that have already fallen sharply since.
- Emissions keep dropping. A 2023 paper is the first to build falling emissions trends into the model — and the answer changes completely: even a full return to replacement-level fertility raises long-run warming by only 0.05°C by 2200.
- Family life already lowers emissions. Moving in with a partner tends to cut personal emissions by roughly as much as going car-free, and a UK study found parents have lower personal emissions than non-parents once income is accounted for.
Restoring replacement-level fertility across Europe would raise long-run warming by around 0.05°C by 2200 — not 0.5, and not by 2100.
BOTTOM LINE
Nobody should feel obliged to have children. But nobody should talk themselves out of it believing it's an environmental sacrifice — the numbers simply don't support that trade-off.
Sources: Wynes & Nicholas (2017) · Murtaugh & Schlax (2009) · fertility/emissions working paper (2023) · UK household carbon study (2010) · Kuruc, population and environmental public goods (2026)