More than half of premature babies have developmental difficulties of varying severity including learning, social and behavioural problems that persist to school age.

With some evidence that stress could impair development of premature babies' brains in the crucial first year of life, Austin Hospital psychologist Jeannette Milgrom designed a program that initially taught parents of 68 premature babies in two Melbourne neonatal intensive care units to recognise signs of stress.

''We were able to show that you can teach parents to interact with their babies differently, they can learn the stress signals of their baby, and we found that resulted in very early gains in development in these babies,'' she said.

''With premature infants the signals are quite varied - it's subtle things like whether the babies are flailing their hands, whether their colour tone is changing and how they are breathing.

''These babies are very susceptible to stress, their nervous systems are not yet fully developed and they experience any environmental change - even having a bath - as quite stressful.''

In nine weekly sessions in hospital followed by a home visit, psychologists taught parents how to care for their babies while respecting their particular needs.

''These babies do interact quite differently from full-term babies - they are not good social partners, they don't make eye contact, they shut down a lot and you need to respect that because that's their way of saying I need time out,'' Professor Milgrom said.

Parents were also taught techniques to soothe babies - including through skin-to-skin contact and gentle massage - and when to employ them.

Babies whose parents received the training had fewer problems with sleep and excessive crying and were better at communicating with their parents at three months compared with babies whose parents did not receive the training.

Researchers also showed improved brain development, as measured on magnetic resonance imaging scans, in babies whose parents received the training.

Professor Milgrom, who presented details of her research at the Australian Psychological Society's annual conference in Perth yesterday, is testing the program in a larger group of 123 babies who are now aged four.

She will follow the children's progress to age six in a bid to show that training parents to respond to stress has resulted in long-term benefits to babies' development.

Already children whose parents received the training have shown promising gains, including improved communication and behaviour, raising the prospect that the training could be offered to parents of all premature babies.

The series of groundbreaking studies could help thousands of infants born early in Australia each year.