An increase in population has seen the lowest recorded levels of births per woman in New Zealand, according to Stats NZ.

The country's total fertility rate in 2017 was down to an average of 1.81 births per woman over their lifetime - which is the lowest fertility rate the country has seen.

Although the number of births increased slightly - 59,610 live births were registered in 2017 which is up 180 from 2016 - the fertility rate still decreased, Stats NZ said.

Despite a low fertility rate, the total New Zealand population continues to grow, driven by near-record levels of migration in 2017, says population statistics senior manager Peter Dolan.

New Zealand's total fertility rate has been relatively stable for the last four decades, ranging from 1.81 births per woman in 2017 to 2.19 in 2008.

"In contrast, fertility rates increased dramatically following the Great Depression and WWII, peaking at 4.31 births per woman in 1961," Mr Dolan said.

The reduction in birth rates since 2008 has been mainly driven by trends among women aged 15-29 years, whose birth rates are now at record lows.

Meanwhile, in 2017, the teenage fertility rate dropped to 15 births for every 1000 women aged 15-19 years - just under half the 2008 rate of 33.

The teenage fertility rate peaked at 69 for every 1000 women in 1972.

- NZ Newswire