The families of two children who were taken into care after medical experts diagnosed Munchausen's syndrome by proxy (MSBP) began a legal challenge to the rulings in the court of appeal today.

The two separate hearings are the first of hundreds of care order cases to reach the court after the government ordered a review of care proceedings based on discredited medical evidence after the conviction of Angela Cannings for murdering her two baby sons was quashed by the court of appeal in December.

The two families are alleging that the children, known only as B and U, were taken into care after their mothers were wrongly diagnosed with MSBP, meaning they allegedly caused or exaggerated their child's illness.

The appeals will be heard by a panel of judges, headed by the president of the high court family division, Dame Elizabeth Butler-Sloss, which is expected to address the issue of whether children who have been living in care should be returned to their families after the courts have ruled that the medical evidence was flawed.

In January the appeal court called a halt to further prosecutions of parents when expert opinion was divided on the cause of death. The court specifically rejected the approach adopted by the retired paediatrician, Professor Sir Roy Meadow, whose rule of thumb was: unless proven otherwise, one cot death is tragedy, two is suspicious, and three is murder. Andrew McFarlane, representing the mother of child U, told the three judges that the message from the Cannings judgment was "if you have a series of unexplained medical traumas, you have three sudden deaths, it does not mean child abuse, it means three unexplained events".

He added that the Cannings appeal did not just involve the evidence of one or two experts but also addressed the "whole process of how courts came to a conclusion as to whether or not child abuse had taken place".

Mr McFarlance said both he and Stephen Cobb QC, representing the mother of child B, would be addressing the standard of proof used in the cases and the relevance of the Cannings judgment.

"It went to the root of the dogma or the fashion, in inverted commas, of looking to see if there are medical explanations for a number of circumstances in a series and after deciding there are not, coming to the conclusion that there must have been some sinister event," said Mr McFarlane.

Dame Elizabeth said that in the Cannings case there was a conflict between the evidence of two sets of experts, with one side saying the children were smothered and the other claiming they could have been victims of cot death. She pointed out that in one of today's appeals there was a consensus among the experts as to the cause of a child's injury.

Mr McFarlane said the principles laid down in the Cannings case regarding the approach to be taken when evaluating expert medical evidence still applied. He said child U had been taken into care after doctors decided that four separate hospital admissions for unexplained and different breathing problems were due to attempted smothering. One of the doctors involved the case said the whole history of the child's illness pointed to "frabricated rather than natural illness".

If there had been one event, it would have been dismissed as purely innocent but because there were four, it was felt to be sinister, said the QC.

"This whole approach has been laid to rest by the Angela Cannings case," said Mr McFarlane.

"Each of the doctors was undertaking the exercise in a way which the judgment says is erroneous."

They had diagnosed that the child's airway was deliberately obstructed even though there were no other symptoms of child abuse such as bruising, said the QC.

Mr McFarlane said that the appeal was not an attack on any of the individual medical practitioners who contributed to the court process. "The issue is much more important and goes to the structure of the approach rather than the clinical work of particular medical practitioners."

The hearings are expected to last two days.