Women who smoke and are overweight are more likely to suffer a stillbirth than non-smoking women of a healthy weight, a report has found.
The Perinatal and Maternal Mortality Review Committee (PMMRC) has released an annual report into maternal deaths and the deaths of babies from 20 weeks gestation to 28 days after birth.
PMMRC chairwoman Dr Sue Belgrave said the report showed it was critical to ensure pregnant women quit smoking and had a healthy weight before and during pregnancy.
"Stillbirth is often unexplained, but where we do know how to reduce risk we need to make sure this information is widely available so women have the opportunity to reduce their own risk of stillbirth.
"Every effort must be made to encourage women to take part in smoking cessation programmes before, during and after pregnancy.
"Likewise, weight-loss before pregnancy is recommended for women who are obese and pregnant women should be encouraged to maintain a healthy diet and monitor their weight gain during pregnancy."
The analysis also showed that women of Indian ethnicity and women having their first baby were at higher risk of stillbirth.
Dr Belgrave said there had been a significant reduction in unexplained stillbirths and deaths of term babies during labour due to a lack of oxygen.
The report found that in 2012 there were 669 deaths of babies aged from 20 weeks gestation to less than 28-days-old, a rate of 10.7 deaths per 1000 births, unchanged from 2007 to 2012.
The report found 19 per cent of those deaths were avoidable.
The report found the main cause of perinatal death in New Zealand is congenital abnormality, which accounts for 30 per cent of deaths.
In 2012, ten women died while pregnant. Two of those deaths were from obstetric complications, and eight from pre-existing health conditions and suicide.
Maori and Pacific women are three times more likely to die while pregnant or up to six weeks after birth than other mothers.
Dr Belgrave said there had been a significant reduction in deaths of term babies during labour due to lack of oxygen.
However, the condition, called neonatal encephalopathy, is significantly higher among babies of Pacific mothers than among babies of New Zealand European mothers.