The teenage birth rate in the wider Whanganui area has almost halved in the past seven years.
New data from Statistics NZ for the Whanganui/Manawatu region shows there were 200 births by mothers aged 19 or under last year, down from 363 in 2008.
This is a rate of 18.7 births per thousand, and the lowest rate in at least 24 years since records were made available in 1991.
Total birth numbers in the Whanganui district increased to 558 after dropping below 500 for the first time in 25 years in 2014.
Birth rates trended down in the past 20 years, but have flattened out in the past five years.
Whanganui Plunket clinical leader Tracey Armstrong said the reduction in the birth rate in the region had been predicted for a long time.
"We've absolutely noticed a drop. It's been steadily decreasing across all the central regions," Ms Armstrong said.
"Statisticians were telling us years ago the birth rate was going to drop.
"I can't pin it to anything. It might just be a societal thing."
Ms Armstrong noted the rise in the number of older mothers.
In the past 25 years, the number of mothers 40 or older giving birth has jumped 250 per cent. The Whanganui/Manawatu region had more than 100 mothers over 40 last year for the fifth time in six years.
College of Midwives midwifery advisor Lesley Dixon said the drift towards births at a later age is to be expected.
"Women are focusing on their careers as a first step and then thinking about having children later. There's also more support from in vitro fertilisation for older women struggling to become pregnant," Ms Dixon said.