Experts are unable to tell if efforts to reduce the number of cot deaths are having any impact

The Government set a national target for reduction in 2017, and ramped up measures to prevent deaths.

The delay in getting coroners' reports on baby deaths - often three years or longer - means experts don't have up to date data.

Infant death researcher Auckland University's Professor Ed Mitchell says funding for initiatives like pepi-pods or wahakura has improved in recent years.

He says DHBs no longer have a supply problem in getting these sleeping devices - but the issue is they don't know if they're working.