New Zealand has the third highest rate of stillbirths of developed countries, a study shows.
The Australia and New Zealand Stillbirth Alliance says some 379 babies are stillborn in New Zealand every year.
The alliance says one third are never fully investigated and the cause remains unknown.
Factors which appear to increase risks are the age of the mother, obesity, smoking and alcohol, the alliance says.
The group estimates a third of stillbirths are caused by doctors failing to detect or respond to complications during pregnancy.
It says unexplained stillbirth is 10 times more common than sudden infant death syndrome.