Motherhood: a boon for the body?

Kim Clijsters made a fairytale comeback by winning the US Open on her return to Grand Slam tennis after giving birth to her daughter. Could child bearing actually be good for both body and mind, and should all new mothers be reaching for their rackets?

Clijsters' success has been seen as adding fresh credence to the theory that pregnancy can in fact enhance sporting prowess, at least among those who had some to start with.

She joins a short, but growing list of elite sportswomen who have pulled off impressive athletic feats not long after becoming mothers.

Few doubt that the demands of motherhood focus the mind as priorities are juggled.

But there is an increasing body of evidence that the biological changes of pregnancy may improve both physical and mental performance.

Blood supply

Pregnancy is itself a physical test.

Almost every organ of the mother's body works harder to accommodate the needs of the growing baby, and blood volume increases dramatically to carry oxygen to the womb.

Once the baby is born, the red blood cells created - rich in haemoglobin - remain in the woman's body for some time, potentially improving oxygen flow to the muscles.

This, in theory, could improve her stamina and the ability to train for longer.

At the same time, the hormone relaxin loosens the hips in preparation for childbirth, but may also give the athlete added flexibility, according to Dr James Pivarnik of Michigan University, who has studied pregnant athletes.

While the exact mechanisms and their impact are still the subject of investigation, the suggestion that pregnancy may have this effect is not new.

In 1988, the First Permanent World Conference on Anti-Doping in Sport included 'abortion doping' on its agenda.

This followed allegations - never substantiated - that East European athletes were being encouraged to get pregnant and abort their foetuses to improve their performance.

The ethics and anti-doping section of UK sport has also raised the issue of pregnancy as a means to legally increase the level of performance-enhancing hormones.

Mental manouevres

There is also the suggestion that the agony of childbirth increases the pain threshold, boosting the mind's ability to cope amid intense physical adversity.

This sounds plausible, although the jury is still very much out in this area. Some research has found that while the threshold may increase dramatically during labour, it returns to original levels in the aftermath.

A study from Bath University found women were wimpier than men when it came to pain. Females felt it sooner, and were able to withstand it for a shorter period.

Indeed it has even been suggested that it may be motherhood itself which makes women more attuned to pain, acutely conscious of any impending problem which could compromise their ability to care.

But on a similar note, it has been suggested that motherhood sharpens mental agility, making a woman more vigilant and alert - key skills on the court.

'Baby brain' or 'preg head' may be a convenient excuse for forgetting names and numbers, but in fact the hormone fluctuations during birth and breastfeeding appear to increase the size of cells in some areas of the brain.

Becoming Kim

For some new mothers feeling fatigued and fat, the suggestion that their bodies are now supercharged may seem risible.

A major review of studies published this summer found - at least when it came to losing weight - sensible eating rather than regular jogging was the key to getting back into shape.

But the Women's Sport and Fitness Foundation says it hopes all mothers can draw some inspiration from Ms Clijsters.

"Our research shows that it's time pressures that stop women taking the exercise they want to," said Harriet Foxwell.

"At one level we need more sports facilities to provide child care. But we also need to find more activities to do with our children - swimming for instance is a good example.

"What was particularly moving was seeing Kim on court with her daughter. Exercise is something we should be able to do together."