Thousands of women who take anti-depressants during pregnancy are endangering their unborn babies, researchers have warned.
The widely prescribed pills have been found drastically to raise the odds of miscarriages, premature birth, autism and life-threatening high blood pressure, they say.
Harvard researchers believe far too many women are taking the drugs during pregnancy because their GPs are not aware of the dangers.
They also suspect that drug companies are trying to play down the risks because anti-depressants are so lucrative to them.
They focused on the complications linked to a group of drugs called selective serotonin reuptake inhibitors (SSRIs), which include Prozac and Seroxat.
Between 2 and 3 per cent of pregnant women in the UK are thought to be on these drugs – up to 19,500 every year.
But the researchers have found that they increase the risk of a miscarriage by 17 per cent and more than double the likelihood of pre-eclampsia – high blood pressure during pregnancy – which can be fatal.
They also double the chances of the baby being born premature, or developing autism.
In addition, the researchers say, the babies are more likely to suffer from heart defects and problems with their bowels.
SSRIs treat depression by boosting the level of the ‘happy hormone’ serotonin in the brain. But the researchers believe that serotonin is also getting into the womb and harming the development of the foetus’s brain, lungs, heart and digestive system.
Dr Adam Urato, assistant professor of obstetrics and gynaecology at Tufts University School of Medicine, in Boston, who was involved in the study, said: ‘I am absolutely concerned – very concerned.
‘We are witnessing a large-scale human experiment. Never before have we chemically altered human foetal development on such a large scale.
'And my concern is why I am trying to get the word out to patients, health care providers, and the public.’
Dr Alice Domar, assistant professor in obstetrics, gynaecology and reproductive biology at Harvard Medical School, said there was little evidence the pills effectively treated depression.
She said GPs were handing out prescriptions for the drugs even though depression could be far better treated through exercise, talking therapies and even yoga.
‘These are probably not particularly safe medicines to take during pregnancy,’ she said. ‘We’re not saying that every pregnant woman should go off her medication.
'Obviously you don’t want a pregnant woman to attempt suicide.’
The researchers, who presented their findings to the annual conference of the American Society for Reproductive Medicine in San Diego, California, have analysed more than 100 existing studies looking at the risks of SSRIs.
Their findings are due to be published next week in the respected journal Human Reproduction.
The researchers say that if women take the pills when they are trying for a baby but come off as soon as they find out they are pregnant, it may be too late.
Dr Urato added: ‘Many of the experts in this area receive funding from the anti-depressant majors. These experts continue to downplay the risks of these agents and to promote the benefits of their use in pregnancy.’
A spokesman for the Association of the British Pharmaceutical Industry said: ‘Clinical decisions about the treatment of depression are complex and must be made by clinicians in consultation with individual patients, regardless of whether or not they are pregnant.’