Hundreds of mothers-to-be are being given drugs to stop them from having obese babies as part of a controversial NHS trial.
The overweight women will take the diabetes pill, metformin, up to three times a day during their pregnancy.
The treatment is designed to reduce the food supply to the baby, rather than make the expectant mother lose weight herself.
The doctors behind the trial say obesity among pregnant women is reaching epidemic proportions and they need to protect the health of tomorrow’s children.
However, many healthy women are likely to be uneasy about mass medication in pregnancy for a problem which can be treated through changes to diet and exercise.
With studies suggesting that the seeds of obesity are sown in the womb, early intervention could save youngsters from a lifetime of weight problems and ill-health.
Metformin, which costs pennies per tablet, has been safely used by diabetics for decades and is cleared for the treatment of diabetes in pregnancy.
The latest figures show that almost half of women of child- bearing age are overweight or obese and more than 15 per cent of pregnant women are obese.
This raises their odds of dying in pregnancy, of their baby being stillborn and of a host of pregnancy complications, some of which can be fatal.
Big babies – those weighing more than 10lb – are around twice as likely to be obese as adults, suggesting obesity is ‘programmed’ in the womb. The metformin trial, which has just started, aims to exploit the ability of the widely used diabetes drug to lower levels of the hormone insulin in the mother’s bloodstream.
Obese women make more insulin than other mothers-to-be and this leads to more fat, sugars and other foods being supplied to the baby.
It is hoped that using metformin to lower levels of insulin will reduce the food supply and cut the odds of babies being born obese.
The treatment may also cut the need for caesarean sections and reduce the odds of pre-eclampsia, a potentially fatal complication of pregnancy.
The trial will involve 400 obese but non-diabetic volunteers at hospitals in Liverpool, Edinburgh and Coventry.
Half will take metformin from around 12 weeks into their pregnancy and half will take dummy drugs.
Their health and their babies’ health will be monitored and the results are expected in four years.
Metformin’s long safety record in the treatment of diabetes means the drug could be prescribed to obese mothers-to-be shortly after this.
Documents for the trial state: ‘Rates of obesity in adults and children are rising exponentially in the UK, as in other developed nations, and there are major causes for concern.
‘The problem of maternal obesity, leading to programming of future life obesity risk in offspring, and manifest by excess birthweight, is reaching epidemic proportions.
‘We believe that metformin will likely be an effective therapy in interrupting this cycle.’
Study leader Jane Norman added: ‘It is absolutely clear that obese pregnant women have an increased risk of a lot of problems.
‘These range from maternal death and stillbirth – which are arguably the very worst things you could have – to increased risk of pre-eclampsia and caesarean sections, and we don’t want to stand by and watch all these happen and do nothing to intervene and not make anything better.’
Professor Norman, of Edinburgh University, said metformin was judged as a safe drug but the trial is needed to ensure the benefits outweighed any risks.
She added that if the trial does show metformin to be of benefit, it is unlikely to work in all women and is most likely to be prescribed alongside advice on diet and exercise.
Dr Ian Campbell, medical director of charity Weight Concern, said: ‘In an ideal world we would be in a position to assist women to be of a near-normal bodyweight prior to conception.
‘But that is not realistic in the current environment.
‘The reality is that many women go through pregnancy carrying too much body fat and it is important we do something about it because it causes serious problems.’