Getty Images / WIRED

Depending on your political inclination, you probably greeted the election of Donald Trump in November 2016 with awe or dismay – or an uneasy combination of both. But Trump’s ascendancy might be responsible for something much weirder: a decline in the number of boys born in Canada’s most populous province.

According to a new study in the scientific journal BMJ Open, Trump’s election was associated with a temporary shift in the sex ratio of newborn babies. But this short-term decline in male babies was only apparent in politically liberal areas of the Canadian province and not in conservative parts.


A relationship between stressful events and the sex ratio of babies might seem implausible, but the pattern is actually well established. Terrorist incidents such as 9/11 and the 2005 London bombings saw a similar shift in the gender balance, which skewed towards girls over baby boys for a few months afterwards.

Ravi Retnakaran, a clinician at Toronto’s Mount Sinai Hospital, usually studies type 2 diabetes but couldn’t resist looking into the link between stressful geopolitical events and sex ratios. Around the time of Trump’s rise to power he just so happened to stumble across several papers exploring the sex ratio at birth after adverse societal events. As the November 2016 result was perceived as so unexpected by many, he wondered if it might have a similar influence as these other events.

Read next This seabed coral farm is trying to save our reefs from extinction This seabed coral farm is trying to save our reefs from extinction

“I felt this apprehension in society that immediately harked back to September 11,” he says. “And that’s when the light dawned in my head, and I wondered if this could have the same sort of effect on the sex ratio.” Retnakaran and his colleague Chang Ye patiently waited for babies to be born so they’d have data to analyse. They looked at all births in Ontario before Trump’s election (April 2010 to October 2016); just afterwards (November 2016 to February 2017); and later on (March 2017 to October 2017).

The team found the lowest ratio of boys to girls occurred in March 2017. This effect was observed in liberal-leaning parts of Ontario, but not in conservative areas. Before Trump’s election, for every girl born in liberal-leaning regions of Ontario, 1.0605 boys were born, but between March 2017 and July 2017 this figure dropped to 1.0217 boys per girl. For conservative-leaning regions there was a slight increase in the ratio, but a statistical analysis showed this was down to chance, not an outside factor.


“We were looking for a very specific signal,” Retnakaran says. “The stratification we did based on liberal-leaning parts compared to conservative-leaning surprised us because we didn't know if that would be there or not.”

You might think the sex ratio at birth would be an even split, but it generally slightly favours males. Around the world, 105 boys are born for every 100 girls. Scientists can’t yet explain quite why that’s the case, although one theory is that because men tend to die younger than women more boys are needed at the start of life.

But at conception the sex ratio is equal – there is no difference in the number of males and females conceived – so the eventual male bias is to do with the probability of miscarriage later in pregnancy being skewed by the foetuses’ sex. “The overall mortality is greater for girls but there are specific windows,” explains Retnakaran. “It’s believed that the common effect that you see after an adverse societal event like an earthquake is reflecting the differential loss of male foetuses within a gestation window of around 20-25 weeks.” That's why three to five months after a stressful event, you may see a fall in the number of boys that are born.

Read next The bees are dying. Can we replace them with flies? The bees are dying. Can we replace them with flies?

But why are male foetuses less equipped to hang on in times of crisis than girls? Fertility expert Allan Pacey from the University of Sheffield says we simply haven’t figured that out yet, though it’s likely to be linked to stress hormones like cortisol. “We do know that stressful events in people's lives, such as terrorism, earthquakes, war, can lead to alterations in the sex ratio,” he says. “But nobody knows the mechanism by which this effect manifests itself.”


Retnakaran’s work chimes with research from the end of 2019 that found pregnant women experiencing physical and psychological stress are less likely to have a boy. Study author Catherine Monk, professor of medical psychology at Columbia University in New York, says this might be explained from an evolutionary standpoint.

“We don’t need as many males to carry a species forward as we do females,” she says. “One man can contribute to reproduction with a lot of different females, so girls are favoured in stressful times.”

But can an upsetting election result really be considered in the same bracket as a natural disaster or terrorist attack? And even if it could, why would Trump’s win have this effect in Canada?

Retnakaran figured the victory for the right-leaning Republican nominee could have global implications and hence be perceived as a stressor in left-leaning nations. And Canada, a historically liberal country with close geographic, economic and socio-political ties to the US might feel this more acutely.

Read next What we know about ACE2, the mystery enzyme behind Covid-19 What we know about ACE2, the mystery enzyme behind Covid-19

“Maybe this research says more about liberals in Ontario. Maybe they should chill out more,” says Pacey. “But if their stress hormones went up in the same way that people react badly to terrorist attacks, then I can see this mechanism operating.”

It’s not the first time Trump’s win has been studied in relation to birth outcomes. Last year, Ralph Catalano and colleagues from the University of California, Berkeley discovered a significant jump in preterm births to Latina mothers living in the US in the nine months following the 2016 political result. “This new work surprises me only because it suggests that Canadians were stressed by the election of Donald Trump. I don't know any epidemiologist qualified to explain that,” Catalano says.

And isn’t the only thing that can affect the sex ratio. There’s a whole host of bizarre suggestions in the scientific literature. Billionaires are more likely to have sons. As are mothers who eat cereal for breakfast. While extreme weather or fasting during Ramadan appears to favour girls.

An important caveat though: Retnakaran’s paper and these similar studies can only establish correlation, not cause. And these are observations at the population level, not the individual. While there are loads of myths about lifestyle changes that can influence a baby’s sex — from a man’s choice of underwear to eating acidic foods — the evidence just isn’t there. The probability of a woman giving birth to a boy or girl will remain the same as a coin toss whatever you do, stresses Pacey.

“I once met a woman who dipped her husband's testicles in hot water every night because she wanted a girl,” he reveals. “The problem is whatever crazy thing that’s tried, 50 per cent will think it worked for them, while the other half will be disappointed.”

Read next Why isn't the UK testing more people for coronavirus? Why isn't the UK testing more people for coronavirus?

More great stories from WIRED

🏙️ A huge Airbnb scam is taking over London

🚙 Thinking of buying an electric car? Read this first

🍅 Why do modern tomatoes taste so bad?


📢 How Slack ruined work

👉 Follow WIRED on Twitter, Instagram, Facebook and LinkedIn