Maternal smoking during pregnancy and bed-sharing with infants create a high risk of Sudden Unexpected Death in Infancy (SUDI), researchers say.
A three-year study, led by Professor Ed Mitchell of Auckland University, has found risk factors identified in the original New Zealand Cot Death Study 30 years ago remain relevant today.
In the three years to February 2015, there were 137 recorded SUDI cases in New Zealand - a national rate of 0.76 per 1000 live births.
The rate was higher for Māori (1.41 per 1000) and Pacific children (1.01).
Despite a major reduction in overall infant mortality, the authors say SUDI continues to be of concern in New Zealand, as the rate is high by international standards.
The study, published in the NZ Medical Journal, was aimed to identify modifiable risk factors.
It found that the biggest risk factor was mothers smoking while pregnant, followed by bed-sharing.
Infants exposed to the "extremely hazardous" combination of both had a markedly increased risk of SUDI, compared with those exposed to neither.
Researchers also said promoting the message to have infants sleep on their backs needed to continue.
Only 21 cases over the three-year period did not involve exposure to maternal smoking, bed-sharing, or front or side-sleeping position.
"Our findings indicate that the prevention messages are still applicable today," the authors said.
"Indeed these findings suggest the prevention messages should be reinforced."
If the identified risks could be avoided, they said, SUDI cases could fall to just seven a year, or about one per 10,000 live births.