NSW women are more likely to have caesarean sections and less likely to smoke during pregnancy or be teen mothers, a new report shows.

NSW women are more likely to give birth by caesarean section and less likely to smoke during pregnancy or have children in their teens, compared to women a few years ago, a new report has shown.

The 2017 Mothers and Babies report, released by the NSW Department of Health, found that women are having children slightly later, with the average age rising from 30.3 in 2013 to 30.7 in 2017.

The age of first-time mothers rose from 28.9 to 29.4 years, the report found.

However, the number of mothers having children in teens dropped from three per cent in 2013 to two per cent in 2017.

Aboriginal or Torres Strait Islander mothers who were teenagers fell significantly, from 17.6 per cent to 12.3 per cent in those four years.

The report found the number of births by caesarean sections in the state has increased by from 31.5 per cent to 33.8.

Mothers who reported smoking at some point during their pregnancy also decreased from 9.7 per cent to 8.8 per cent.

"Less smoking in pregnancy, fewer teenage pregnancies and earlier antenatal care all contribute to a healthy start to life for NSW children," the Department of Health's Professor Michael Nicholl said.

The report also found women who gave birth in 2017 were less likely to have been born in Australia, when compared with 2013.

The percentage of such mothers born in Australia decreased between from 65.1 per cent to 61.6 per cent in that time.

In 2017 women from India accounted for 4.7 per cent of all women giving birth in Australia, while women from China accounted for 4.6 per cent.