We have long been obsessed with how women’s bodies and health are altered by motherhood — what it does to their hormones, brain power, relationships and even their risk of cancer and other diseases.
But while men might not go through the physical process of childbirth, a growing body of evidence suggests they, too, experience physical and psychological transformations when they become fathers.
Last month, a study of 624 men found their testosterone levels dropped by one third when their children are born. The researchers at Northwestern University in Chicago said this drop causes men to become less aggressive and display a more caring side.
‘While pregnancy causes profound changes in women, this is more subtle level in men,’ says Dr Allan Pacey, a fertility expert at the University of Sheffield.
Dr Craig Garfield, an assistant professor of paediatrics at Northwestern University, says: ‘We’re just beginning to understand the contributions fatherhood makes to men’s health. Some research seems to show benefits, while some shows risks. It’s exciting.’
Here, experts reveal the surprising effects fatherhood has on the male body and brain.
Perhaps one of the most intriguing findings about fatherhood is how it affects men’s personality. The latest U.S. research found levels of testosterone dropped by 34 per cent after their partners gave birth.
Testosterone is associated with dominant and aggressive behaviour, and researchers concluded a fall in the hormone could show men are ‘hard-wired’ for parenthood, just like women.
They have evolved to protect their babies and their genes by becoming softer and more caring when their offspring arrive.
Dr Pacey explains: ‘A drop in testosterone doesn’t make a man more child-friendly, but it switches his priorities to invest in the new infant. It would be interesting to find out if the same thing happens in stepfathers.
‘Is this fall in testosterone caused by the presence of a child and sense of social responsibility or is it down to smells and hormones telling you this is your offspring?’
In our primate relatives, at least, it seems the latter is true. Another group of U.S. scientists studied male marmosets, one of the few primates other than humans in which both genders share the care of their offspring. When they gave the males a whiff of their babies’ scent, their testosterone levels dropped within 20 minutes.
Dr Garfield says more investigation is needed into how such a hormonal shift might affect men’s health. ‘We know hormones from pregnancy and breastfeeding protect women from some cancers, such as breast and ovarian; it’s possible hormonal shifts in men may be protective of men’s health, too.’
However, some experts say the reason for fluctuating testosterone is less complicated…it could be a physical response to stress.
‘In fathers, the hormone cortisol tends to go up around their partner’s pregnancy,’ says Dr Mark Vanderpump, an endocrinologist at the Royal Free Hampstead NHS Trust in London. ‘Cortisol is the stress hormone and its chief role is to keep your blood pressure up when you’re going through acute stress. But as cortisol rises, it also reduces testosterone production.
‘Their partner’s pregnancy may be an example of a stressful event, so whether the drop in testosterone is specific to evolution is not clear.’
Any dad will tell you their priorities shifted when their baby came along and some scientists think fathers’ brains actually works differently.
In 2006, researchers at Princeton University examined the brains of male marmosets and found that after childbirth the connections between the brain cells were more effective in the prefrontal cortex — the part of the brain responsible for planning and memory.
Since these are skills new parents would need, the researchers concluded that a similar boost may happen in the human brain. A later study by the same team also found fatherhood generated new cells and connections in the hippocampus region of the brain in male mice — the area associated with the processing of emotion.
The average father-to-be gains a stone during his partner’s pregnancy, a 2009 poll of 5,000 men found. About 40 per cent blamed the extra snacks in the house because of their partner’s bigger appetite, while others reported being served larger portions or said they ate more to make their partner feel better about getting bigger.
However, there might be more to it, as this behaviour can also be seen in the male marmoset, which gains up to 20 per cent of their body weight during their mate’s pregnancy. The male monkey grows a pregnancy paunch in preparation for the extra energy they’ll expend when the baby arrives.
One in four expectant fathers experiences many of the pregnancy ‘symptoms’ of their female partners, a recent survey of 2,000 men found.
They reported food cravings, mood swings and nausea — some even complained of phantom pregnancy pains.
It is thought modern man’s greater involvement in the pregnancy (more fathers now attend antenatal classes and scans) is to blame for ‘pregmancy’.
‘Society now expects men to have an interest in their baby and to know what their partner is going through,’ says social psychologist Dr Sandra Wheatley. ‘When they go to scans becomes more real for them — just as it does for a woman. So it’s not surprising they start to experience psychosomatic symptoms.’
She adds that so-called sympathy symptoms might be the physical result of a man’s anxiety over his partner’s pain.
‘We often see this in people living with cancer patients: they exhibit their anxiety about their loved one’s health as a physical symptom, such as nausea.’
In a study published last month in the journal Human Reproduction, U.S. scientists looked at 135,000 men and found those who did not have children were 17 per cent more likely to die from a heart condition.
Why would this be so? Dr Ian Banks, visiting professor of men’s health in Europe at Leeds Metropolitan University, believes it is down to lifestyle.
‘When men have kids, they start to think about living longer. They change their diet, they give up smoking, they stop going to see their mates at the pub as much.’
He points to a successful public campaign to stop heart disease, which showed family photographs with the father missing. ‘That had a real impact,’ he says.
He adds that while single, childless men are unlikely to visit their GP, once they have offspring they come into contact with doctors more — giving GPs a chance to talk to them about their own health.
Testosterone is linked to sex drive and it’s thought the hormone shift after pregnancy might make a man more monogamous.
‘Testosterone levels dropping would cause a drop in libido, so the man is less interested in sex,’ says Dr Pacey. ‘This makes sense because the partner will be less interested in getting back to the routine, and it lessens the risk he’ll start to look elsewhere.’
Last month’s study suggested the effect wasn’t permanent and that, as the child grew up, men’s testosterone levels rose again.
Meanwhile, animal studies at the University of California found male monkeys become more sensitive to vasopressin after becoming fathers. Vasopressin, a hormone produced in the pituitary gland in the brain, is thought to trigger feelings of bonding between a male and his mate.
Men are just as likely to suffer from postnatal depression as women, a study found last year.
The East Virginia Medical School reviewed 43 studies from 16 countries, and found one in ten fathers — the same ratio as mothers — was likely to suffer before or after the birth.
‘I call it the male baby blues,’ says Dr Roger Henderson, a GP and the author of a new book, Dad’s Guide To Pregnancy For Dummies. ‘It can be a real relationship wrecker.’
The problem could be the drop in testosterone, a hormone linked to sex drive and energy. ‘I see a lot of men who can get psychologically fatigued — a low testosterone level can cause that,’ says Dr Henderson.
Other risk factors include the displacement of the father’s place in the home and a traumatic birth.
Men are most likely to experience problems three to six months after the baby’s birth. While a woman’s body and lifestyle changes the moment she is pregnant, her partner often works right up to the birth, so has no time to prepare emotionally for the new arrival.
‘Men get a sudden realisation that everything’s going to be different,’ Dr Banks explains. ‘But they don’t discuss it. I used to work in obstetrics and the number of guys I’d see dying to have a cry — it’s no surprise these suppressed emotion leads to depression.’
He advises women to encourage their partner to talk.
‘Men have no tools to cope and there’s no education for them.’
by Susan Floyd