Australia has reported its lowest birth rate in more than a decade, as the average age of first-time parents continues to increase.

The country's birth rate fell significantly between 2007 and 2020, from 66 per 1000 people, to 56 per 1000 people.

As for the first few months of the COVID-19 pandemic, the number of babies born declined by about 7100 between 2019 and 2020, equating to a more than two per cent drop, according to a report by the Australian Institute of Health and Welfare published on Friday.

The average age for giving birth rose from 30 in 2010 to 30.9, with the proportion of teenage parents falling from 3.8 to 1.8 per cent in the decade to 2020.

The proportion of parents aged 40 and over also went up slightly to 4.5 per cent in 2020.

Parents aged 40 and over more commonly delivered via caesarean sections.

Overall, caesarean sections accounted for more than one in three births in 2020, up by five per cent in the previous decade.

In 2020, nearly one in eight expectant parents accessed antenatal care in their first trimester of pregnancy, which was an increase of 16 per cent since 2012.

That wasn't the case in remote areas, where the proportion of parents accessing that care in their first trimester hovered about 70 per cent, institute spokeswoman Deanna Eldridge noted.

More than nine in 10 of the nearly 296,000 babies born in Australia in 2020 were born at term and a healthy weight.

However, in the past decade, the rate of stillbirths and neonatal deaths remained between seven per cent and eight per cent for every 1000 births, and between two per cent and three per cent for every 1000 live births.

"One of the most amazing and challenging times in a family is pregnancy and the welcoming of a new baby, but tragically some families experience the loss of their baby," Ms Eldridge said.

Congenital anomaly was the most common cause of perinatal death in 2019.

The number of expectant parents who reported smoking at some stage during their pregnancy dropped from 14 per cent to more than nine per cent in the decade to 2020.

The Australian Institute of Health and Welfare, which published the birth findings on Friday, is expected to release a more detailed report about still births and neonatal deaths in November.