By Paul Rincon
BBC News science reporter, St Louis
Placing children in long-term care is in itself "an act of abuse", according to a leading professor of paediatrics.
Speaking at a science conference in St Louis, US, Professor Dana Johnson said that even a week in an institution could be detrimental.
The University of Minnesota scientist said that children placed in these facilities could suffer serious physical and emotional health problems.
The findings come from an ongoing study of children conducted in Romania.
Professor Johnson, from Minnesota Children's Hospital, said long-term institutional care should be a last resort, and then only with a view to placing children with foster families.
But he explained that in the Bucharest Project, children placed in a more nurturing environment showed considerable improvement.
"The conclusions are that nothing replaces a family," Professor Johnson told the BBC.
"Children in institutional care have deteriorations in many things that we want to see children improve in during the earliest years of their life," he said.
"Their cognitive abilities are lower, their growth is terrible and their brain development is abnormal as well."
What is even more surprising is that Professor Johnson puts the problems down to emotional deprivation affecting the children's hormonal balance.
The study found that children in institutions fall behind the norm in terms of their stature, brain and weight.
"As children get to two or three years of age, their weight starts to recover, but their height continues to deteriorate," Professor Johnson said.
"So up until puberty, you can predict how short children are going to be by the time they have been in the orphanage. They lose about one month of linear growth - or stature - for every three months they have spent in the orphanage.
"I think putting a child in long-term institutional care is an act of abuse."
Professor Johnson would like to see an end to all long-term care institutions for children.
"There is always going to be a place for short-term facilities. But I think we need to underline 'short-term'. These kids cannot stay in those facilities for longer than necessary.
"A few days in an institution should be as long as children are asked to endure," he added.
"Children need to be in a family; they need it for their physical and brain development to be in a nurturing environment," Professor Johnson said.
Details of the research were presented at the American Association for the Advancement of Science annual meeting.