Health professionals and the police have admitted mistakes after Petrina Stocker was found guilty of killing her nine-year-old son David.
Petrina Stocker poisoned her nine-year-old son, David, with salt
Stocker was convicted of David's manslaughter after she put salt in his hospital drip feed.
David, who had been ill, died in Great Ormond Street Hospital in August 2001
After Stocker's conviction on Thursday, hospitals and police connected with the case said they would learn lessons from the events which led up to the tragedy.
Dr Jane Collins, chief executive of Great Ormond Street Hospital for Children NHS Trust, admitted there had been a failure to stop it happening.
But she warned a London news conference: "We have put more blocks in the way, but there's always the possibility that it might happen."
Dr Collins said the hospital felt great sadness at David's suffering and death, and there was deep regret that he died while under their care. "The vast majority of parents love their sick children, they want to be with them, and to help with their care. Working with parents is central to what we do.
"Unfortunately, child abuse exists and Fabricated or Induced Illness (FII) is a particularly complex form of abuse to identify. Every member of staff needs to be alert to that small possibility of a determined parent deliberately harming their child."
'Always think the unthinkable'
Marilyn Richards, executive director, social services for the London borough of Havering, said: "I would openly acknowledge that at the time, we made a serious mistake, in that we didn't complete an assessment of David, when we were required to do so, after the strategy meeting, in April/May time.
"We had expectations that social workers would have contact with David, that didn't happen, these were mistakes which took place at my agency."
She said there had been difficulties then, which had now been rectified.
She said there had been some shortfalls in the quality of children's social services in Havering at that time, but these had now been addressed.
Mark Rees, chief executive of Barking, Havering and Redbridge Hospitals NHS Trust, which manages Oldchurch Hospital, said: "What this dreadful case has reminded us is that we must always think the unthinkable, even though the thought that a mother could kill her child goes against the culture of every professional in the NHS.
"Hospitals are places where we treat and care for the sick, not where we expect to see a parent kill their own child.
"We are confident now that with new child protection arrangements in place, every professional knows how to trigger help from an expert at any time of the day or night if there are suspicions.
'Death was very quick'
"We will involve our colleagues in social services and the police if necessary at an early stage."
Det Ch Supt Peter Spindler, head of child abuse investigations for the Metropolitan Police, said: "One of the difficulties is that FII (fabricated induced illness) usually takes place over some years. In this case David's death was very quick, after four months.
"Our officers were working in the normal way, with both health and social services, but I accept we were probably not robust enough in the way we managed that investigation."
The agencies said each organisation involved in David's care has already brought in new measures to protect children, and an action plan includes requirements such as ensuring all staff focus on the child, and offer him or her advocacy and help, and that they should involve senior staff in all cases where FII is suspected and access a psychiatric opinion.