A new study from the UK shows that as many as half of the deaths could be prevented.

Sophie Bissmark doesn't have many photographs of her daughter. She thought she would have years, but Neve died at just 13 weeks old.

Although Sophie wasn't sleeping with Neve at the time, it hasn't stopped her questioning what happened.

"Cot death didn't happen to people like me. I wasn't young, I didn't smoke, that's as far as I thought the risks really were. I was breastfeeding and I would definitely feed in bed, then she'd fall asleep. Often than not I would like to put her back in her cot but if she'd cried I'd put her back in bed with us," Bissmark said.

Experts are now advising against sleeping with a baby no matter their age.

Researchers analyzed 80 cot deaths and found that more than half happened while the baby was sleeping with a parent.

Nearly a fifth were on a sofa, 17 percent, and 20 percent were found with a pillow.

"It confirms that the safest place for a baby to sleep is in a cot [or crib] by the side of the bed or near the parents," Joyce Epstein said. Epstein is with an infant death charity.

Bissmark went on to have a son and she now helps other parents.

Researchers believe all the advice of the last 20 years has helped cut the number of cot deaths, but they now think they have the evidence to show more lives could be saved.