Data from the Australian Bureau of Statistics (ABS) has shown that in Warrnambool and the south-west the fertility rate was 1.8 per cent per woman in 2022.

In 2022 the national fertility rate was 1.63 births per woman, which was lower than the 2021 rate of 1.7 births per woman.

The total fertility rate has remained lower than the replacement rate - considered to be 2.1 babies per woman to replace her and her partner, in the absence of overseas migration - since 1976.

For Mrs Williamson the decision for her and husband Trent to add another child to their family was a no-brainer.

"For me it just felt like someone was missing," she said.

Mrs Williamson also has a seven-year-old daughter Kaytie and a four-year-old son Arlo.

She said the age gaps had made the transition to a family of five reasonably smooth, with Kaytie and Arlo old enough to offer some help.

"They're very hands-on and helpful," she said.

"As the saying goes 'many hands make light work'."

According to the ABS data, there were 1474 babies born in Warrnambool and the south-west in 2012.

The median age of the mothers was 29.8 and there were 1282 babies born in 2022, with the median age of mothers 30.6.

Leading demographer Bernard Salt said the birth rate was falling nationally because young people were making a choice to have smaller families in order to improve their chances of buying a house and providing a lifestyle.

"Instead of having three or four kids they might have two kids," he said.

"This is a national trend that has been in train for quite sometime but with a birth rate of 1.8 (in Warrnambool and the south-west) it is above the national average and we tend to find this in rural and regional communities where it is cheaper to buy a home and live the quality of life that people want for a family.

"If you're kind of family focused and orientated then maybe the south-west and Warrnambool is a place to consider.

"I'm sure there are very expensive houses there but in comparison they're more affordable than elsewhere.

"In some respects you could argue maybe this is a plus for Warrnambool, in the sense of 'we offer quality of life for a family... have opportunities and jobs and all the amenities of a larger town' - Warrnambool is the place to be."

Mr Salt was born in Terang and grew up in a family of six.

He said growing up there were many larger families including a couple of families with 12 children.

"There were those big farming families," he said.

"There are still very large families in Australia and they tend often to be attached to migrant communities.

"Certainly in places like the south-west the family sizes have decreased but it's decreasing from a high base and it's still more family orientated than say the Australian average or a place like Melbourne and Sydney.

"Yes the birthrate is decreasing but I regard it as a vote of confidence in Warrnambool and the south-west as a family friendly location.

"It's something the region should be proud of I think."

ABS head of demography Emily Walter said the data continued a trend in births over the last 40 years, with the average age of both mothers and fathers steadily increasing since the mid 1970s.

"In 1975, less than 20 per cent of births were to mothers who were between 30 and 39 years old, but now nearly 60 per cent of births are to mothers in this age group."

She said although total fertility remained low, the fertility rate for women in their late 30s and early 40s had significantly increased.

"From 1991 to 2022, the fertility rate of mothers aged 35-39 years has almost doubled from 36.0 to 69.3 births per 1000 women, and for mothers aged 40-44 years, it has nearly tripled from 5.5 to 15.8 births per 1000 women," she said.

"In contrast, the fertility rate of teenage mothers has reached an all-time low of 6.8 births per 1000 women, from 22.1 births per 1000 women in 1991."

In 2022: