Karen, Birmingham Social Services said, had Munchausen Syndrome By Proxy, the mental illness that causes parents to harm their children in an attempt to draw attention to themselves. Her child had been placed on the 'at risk' register even before she was born in December 1999.

Proof that Karen had MSBP was provided by Professor Sir Roy Meadow, the paediatrician who came up with the theory in 1977 and, until he was recently discredited, was regarded as the world authority on the condition.

Meadow had studied Karen's files and, although he had never met her, he warned it was likely she would abuse her baby.

Meadow's evidence was based on what had happened to Karen's son, Michael. The child had been born with breathing difficulties and had been taken to hospital on several occasions following serious attacks. Michael died in Birmingham Children's Hospital in January 1999, two days after being admitted because of shakes and a pale complexion. It transpired he had suffered acute brain damage and it was left to his parents to decide to switch off his life-support system. He was four months old.

The one thing that helped the couple cope with the tragedy was the fact that, soon after Michael's death, Karen became pregnant again. 'We didn't have a clue there was a problem until the letter from social services dropped on the doormat,' Karen, 38, said. 'It said the child was to be placed on the "at risk" register. At first I had no idea what they were going on about.'

They appealed against the decision but a High Court ruling in October 2001 cleared the way for the child to be adopted. This was despite the fact a judge had consulted a panel of seven expert witnesses, five of whom said they believed Michael had died of natural causes. The remaining two experts - including Meadow - said the most likely cause of death was smothering. The judge sided with the minority.

And here the story would have ended, leaving Karen branded a child abuser and a woman afraid to have any more children.

But, following the discrediting of MSBP, paediatricians and psychologists are now having to reinvestigate child abuse claims and Karen's case is just one of many which have raised concerns.

Unknown to his parents, Michael suffered from a serious heart condition. This should have meant that doctors ruled out treating him with a number of drugs, including one called cisapride, once commonly used to treat digestive problems but since taken off the market in the US and the UK after it was linked to a number of deaths.

Michael was prescribed a course of cisapride on two occasions. Following the second course his parents took him off it because he wasn't dealing well with the side-effects. Experts say the drug interferes with the cardiac rhythm and has been known to induce a near-death experience in children, something that could be confused with an attempt to smother them.

The drug's makers, Janssen Pharmaceutica, declined to comment last week. But the company acknowledges that the drug shouldn't be prescribed to certain patients.

A statement made by Janssen four years ago read: 'Because of the risk of serious cardiac arrhythmias and death associated with the use of Propulsid (cisapride) in certain patients, Janssen ... has decided to discontinue marketing Propulsid as of 14 July, 2000 ... Propulsid has been associated with serious cardiac arrhythmias.'

Karen is now demanding an inquest to establish whether cisapride was responsible for her son's death. 'My son had a hole in the heart. He should never have been given the drug in the first place,' she said. 'On the day that he went into hospital he hadn't eaten anything as he wasn't feeling well. We only found out later that he had been given a dosage of cisapride in hospital shortly before he had died. Why should he be given a digestive drug when he's not eating?'

It is a question that seems to trouble Janssen, too. The company wrote to the West Midlands Centre for Adverse Drug Reaction Reporting to ask whether any doctors who had been treating the baby had filed an adverse reaction report on the drug.

Chances are that Janssen may have to file more adverse reaction inquiries in the months to come. Anti-MSBP campaigners in the UK claim there is a clear correlation between the prescription of the drug and false allegations of child abuse - usually those involving smothering. They claim that more than 150 women whose children were taking cisapride were wrongly diagnosed as having MSBP.

One doctor in Australia, Professor Colin Morley, has gone as far as to estimate that in almost every such case he has been involved in, the child was on cisapride.

Following the Government's decision to re-examine hundreds of cases involving MSBP, the prescription of cisapride is to undergo acute legal and scientific scrutiny in the courts.

But the danger is that cisapride - like MSBP - becomes a catch-all explanation for child abuse; one that blinds all those involved to the real cause. Child psychologists and scientists point out that other drugs and illnesses cause symptoms that can be mistaken for abuse and there is an urgent need for these to be investigated.

Nevertheless, as one doctor put it: 'We don't know the true picture surrounding allegations of child abuse. But what we do know is that there has been a marked decline in the number of cases involving Munchausen's since cisapride was taken off the market.'