The only link most of us make between our birthdays and how much we weigh probably rests on the amount of Colin the Caterpillar consumed once the candles have been blown out. But could the season in which you were conceived actually be to blame?
It might sound as far-fetched as pinning your life chances on your star sign, but academic studies are increasingly suggesting a connection between when we were conceived or born and our adult lives — from our health to how successful and sporty we are.
So what does the research say and does the timing of your conception or birth have more influence than, say, your actual choices? Read on.
Winter conception? You’re more likely to be slim
I’ve never had much cause to boast (or indeed think) about having been conceived in winter but that may be about to change. New research from the University of Tokyo has suggested that conception during the colder months (October 17 to April 15) means a person has more active brown fat adipose tissue — the type of fat that burns calories to keep us warm and helps to regulate blood sugar. In people who are deemed overweight or obese, brown fat activity is often lower.
The observational study, which made headlines last week, also concluded that a cold conception was linked to lower BMI, less fat accumulation around the organs and better overall metabolic health.
It’s thought the wintery environment could have a genetic impact (known as epigenetic modification) on sperm or eggs, which is then passed along when they meet. As the lead scientist Takeshi Yoneshiro put it: “Our study suggests that the environment experienced by parents even before pregnancy can shape the child’s metabolic health later in life.”
So should we all be trying to conceive during winter (as my son was — not to brag, naturally) and taking ice baths? Not enough is known to draw firm lifestyle conclusions, but scientists say the study could improve our understanding of rising rates of metabolic disorders such as high blood pressure and diabetes, and offer insight into the challenges climate change may pose in keeping us healthy.
Summer babies: bigger and better?
In schooling terms, June, July and August can be considered the worst months to be born, with summer pupils so much younger than their wintery peers. But all isn’t lost: in 2015 researchers from the University of Cambridge found that summer-born folk are likely to be taller as adults. The analysis of 450,000 people in the UK also concluded that summertime baby girls were likely to hit puberty and get their periods later, which can be an indicator of better health in later life. Babies born in December, January and February showed the opposite traits.
It could all be down to health-giving vitamin D, with these women exposed to more sunlight during the second trimester of their pregnancy (a vitamin D deficiency has been linked to bone problems and rickets in children). The NHS recommends that pregnant and breastfeeding women take a daily supplement containing 10mcg of vitamin D every day between September and March, when the sun is at its shyest.
September birthday? Score!
What do Wayne Rooney, Pelé, Maradona, Ryan Giggs and the Brazilian star Ronaldo have in common — along with many other top-flight footballers? They were born between September and November.
We’re familiar with the idea that children born early in the school year can do better academically, but they may also have a higher chance of making it in professional sports. A 2021 analysis of British players in the Premier League and Championship found that those born in the first three months of the school year were almost twice as likely to become top footballers compared with those born between June and August. Players are twice as likely to be in the National Football Museum’s hall of fame if born from September to November. The same patterns have been observed in professional running, Canadian ice hockey and at the 2008 Beijing Olympics.
This autumn bias has been attributed to the “relative age effect” — simply, that children born earlier in the school year are quicker to mature physically and more likely to be picked for teams or specialist coaching. Just don’t tell Lionel Messi, a 5’7” June baby…
January: a bad egg?
Ever considered that your food allergy could be traced back to your moment of conception? Me neither, funnily enough. Except, scientists at Oulu University in Finland have suggested that babies conceived in January and February have an 11 per cent risk of developing a food allergy — predominantly milk or eggs — compared with a 6 per cent risk for those conceived in September and October. The 11th week of gestation was found to be key: a period of time when babies conceived in winter may be exposed to increased levels of birch and alder pollen in the spring air. Those same babies may also have higher levels of asthma when born in the autumn as they stay indoors more in their first few weeks of life and can be exposed to allergens such as dust mites. As a January baby, I’m itching just thinking about it.
Is spring the worst time to be born?
The daffodils are in bloom and trees in blossom, but spring has a bad reputation as a birth season. Adults born between March and May have been labelled as more likely to suffer with health problems, from autism to schizophrenia, diabetes, heart failure and Parkinson’s. According to a 2011 study published in the British Journal of Psychiatry, spring babies were 15 per cent more likely to develop anorexia. Scientists at the University of Bristol found that spring children were more “sluggish” while German researchers concluded they may not live as long. Blimey.
The truth? We simply don’t know for sure. Academics have hypothesised that factors such as a lack of sunlight in utero, fewer fresh vegetables during the third trimester of pregnancy and the mother catching winter flu could all have an impact on the health of spring babies. But there are still too many unknowns to conclusively say spring is the worst time to be born. And besides, a 2014 Hungarian study found that those with spring birthdays are likely to have a hyperthymic — overly positive — temperament. Guess you would have to, eh?
