Co-sleeping is where the baby is shares a bed with his or her parents.

However, research so far has produced contradictory findings.

Some studies suggest that co-sleeping cuts the risk of cot death - or sudden infant death syndrome (SIDS) - while others indicate that it increases the risk.

Researchers from Durham University's department of anthropology now want to determine exactly what role co-sleeping plays in the syndrome.

They are seeking 250 sets of parents to take part in a study monitoring the effects of co-sleeping.

Their first task will be to develop an "inventory" of co-sleeping habits.

Definition

Dr Helen Ball, director of the project and a lecturer in anthropology at the university, said people slept with their children in different ways.

She said the project, which is set to last for two years, would look at the strategies parents use to ensure a good night's sleep.

It would look at the safety issues involved, and its findings would be used by the Foundation for the Study of Infant Deaths, which is funding the project, to produce guidelines.

Joyce Epstein, who is secretary-general of the foundation, said guidelines had been difficult to produce due to the confusing findings of earlier studies.

These were down to a vague definition of co-sleeping.

"Sometimes it means taking your baby to bed with you all night, every night. Sometimes it's only for part of the night, sometimes it's only part of some nights."

Some parents only shared their bed with their baby when the baby was ill, and some only when their baby was playful, she said.

"We want to develop an inventory of the different bed-sharing practices that exist," she said.

Ms Epstein said this would allow other researchers to fully explain what they mean by co-sleeping.

It may turn out that some types of bed-sharing practice are beneficial and some harmful.

Non-intrusive observation

The study will use new technology to monitor the participants.

Participants will have their sleeping patterns monitored

Infrared cameras will monitor their night-time behaviour and will allow the researchers to identify different types of co-sleeping without intruding into peoples' homes.

Dr Ball said that parents would be free to pull out of the project if they were not happy with being monitored, but added that the team had taken steps to ensure privacy was respected.

Ms Epstein said that anthropology played a large part in defining the foundation's approach to the syndrome.

"David Attenborough knows more about how wild animals rear their young than we know about how humans rear their young. That's what we're trying to find out."

The study is part of wider-ranging research project run by the Foundation for the Study of Infant Deaths, which aims to look at a range of factors that affect an infant's general health.

Last year, 463 babies died of SIDS in the UK, but nobody knows what causes it, and the foundation runs 25 projects around the UK to try and determine the reasons behind the syndrome.

It will look at all aspects of child care and infant health, as cot deaths appear to be linked to general health.

Surprising finding

Ms Epstein said: "The advice we've been giving out to help avoid cot death turned out - surprisingly - to help prevent other kinds of illness.

"Cot death is not so different from other things that can go wrong with babies.

"We want to look at the larger picture - not just how and why babies die, but how and why babies get ill.