A quarter of Australian women giving birth are aged 35 or over

One-quarter of Australian women giving birth are aged 35 or over, with 29% of those being first-time mothers.

The number of babies born to older mothers has been increasing over time, data published by the Australian Institute of Health and Welfare on Thursday shows. The latest data, from 2019, shows there were more than 76,000 babies born to mothers aged 35 or over, compared with almost 69,000 in 2009, and 42,000 in 1999.

Since 1999 the rate of women aged 40–44 giving birth has almost doubled, with 15.5 mothers per 1,000 in 2019 compared with 8.4 mothers per 1,000 women in 1999. The rate almost quadrupled among women 45–49, with 1.1 mothers per 1,000 women in 2019 compared with 0.3 mothers in 1999.

More than half – 55% – of mothers aged 40 and over gave birth by caesarean section in 2019.

AIHW spokeswoman Bernice Cropper said the average maternal age increased from 27.1 years in 1979 to 30.8 years in 2019.

“There can be advantages to giving birth later in life and the majority of older mothers will have uncomplicated pregnancies and healthy babies,” she said.

Older mothers were less likely than younger mothers to smoke, and they were are also more likely to live in major cities and less likely to live in low socioeconomic areas.

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Generally, risk factors and outcomes were similar for mothers aged 35–39 and 20–34, “but mothers aged 40 and over were a little more likely to have a baby born pre-term or requiring admission to a special care nursery”, Cropper said.

“Women who give birth later in life are more at risk of complications, such as gestational diabetes during pregnancy and birth. Other complications include increased risk of gestational hypertension, pre-term birth and low birthweight babies. This is particularly seen for women giving birth for the first time.”

Older mothers are defined by the institute as those aged 35 years or older when they give birth. Older mothers were more likely to be born overseas, and less likely to be Aboriginal or Torres Strait Islander, than younger mothers, the report found.

Prof Hannah Dahlen, from Western Sydney University’s school of nursing and midwifery, said it was important to examine the most recent years of data from the Institute which shows the average age of mothers giving birth is starting to level out with a 0.1 increase, from 30.7 years in 2018 to 30.8 years in 2019.

“In the past decade the average age has increased by 0.8 years, from 29.9 years in 2008,” Dahlen said. She said comparing 2019 data to 1999 data would misrepresent this more recent trend.

She added that the high cesarean rate in women over 40 could not be explained or justified by the fact that giving birth as an older woman can come with more risks, and that many older women have uncomplicated births and healthy babies.

“While statistically, women over the age of 35 are more likely to develop diabetes and high blood pressure, you can have very unhealthy, overweight 23-year-olds, and very healthy 35 or 40-year-olds with none of those health conditions,” she said.

She added that older age of mothers was often used to justify increasing rates of interventions like caesarean, but this was “a convenient excuse”. Her research has found caesareans are increasing in young, healthy women with no complications as well. But her research has found caesareans can be associated with childhood health problems and higher rates of hypothermia following birth.

“It is important women don’t think there is a magical tally so that once you hit 35 your body fails you and your body falls to pieces and requires you to need interventions like a caesarean,” Dahlen said. “We must treat all women as individuals.”

Dahlen said older women were more likely to be in the private sector where the caesarean section rate is nearly double that in the public sector.

“But we have also seen older women have home births, or giving birth in birthing centres, without these interventions and they have perfectly good outcomes, and they have a similar profile to women who go through the private system,” she said.