As Australians get bigger, more pregnant women are technically obese

More women are giving birth while statistically obese, a trend researchers say could have serious effects on the health of them and their babies.

The debate continues around what constitutes a healthy weight – since 2009, Deakin University and Western Health researchers have been able to measure the body mass index (BMI) of pregnant women in Victoria.

Kerryn Cugley, with her daughter Amity, is pregnant with her second child and says having non-judgmental medical support has made this pregnancy much easier.Credit: Simon Schluter

Statewide, rates of obesity among pregnant women – who are weighed during their first prenatal appointment – have risen steadily to more than one in five between 2010 and 2019, while pregnant women with severe obesity jumped by 65 per cent, the research has found.

Of 710,364 births, the proportion of mothers with what is considered “normal” BMI declined from about 50 per cent in 2009 to 46.8 per cent in 2019.

The body mass index is a formula based on height and weight, the healthy range of which is considered to be between 18.5 and 25.

As someone who has lived in a larger body, midwife and researcher Professor Linda Sweet said she understood the importance of reducing stigma, especially because it helped women with a higher BMI feel they could engage with medical services. But she said the upward trajectory of pregnant women’s BMI carried concerning risks.

“Obesity increases the risk of gestational diabetes, high blood pressure, blood clots and unplanned caesarean sections,” she said. There is also an increased chance of stillbirth, premature birth and birth-related trauma for mother and baby, she added.

Sweet is the chair of midwifery at Deakin University and Western Health. She said lifestyle and other factors contributed to increasing BMI, but the study published in the Medical Journal of Australia showed the highest rates of maternal obesity were in regions where health services were more difficult to access.

Midwifery professor Linda Sweet, of Western Health and Deakin University, said women in Victoria’s regions need better access to services designed to support mothers living with obesity.Credit: Penny Stephens

The only part of Victoria where maternal obesity had not increased was a small area in Melbourne’s inner east, possibly partly because health literacy, affluence and access to health services were higher, she said.

The Mallee, which has the highest level of economic disadvantage, also had the largest increase in obesity among pregnant women, from 24.5 per cent in 2010 to 31.8 per cent in 2019.

Dr Lauren De Luca, director of maternity services at Western Health, said the rates of women who are considered overweight or obese were increasing across Australia.

Australian Bureau of Statistics data shows the weight of the average Australian woman rose from 67 kilograms in 1995 to 72 kilograms in 2017-18 (the average weight of men rose from 82 to 87 kilograms).

In 2022, the ABS found 72.1 per cent of women – and 63.5 per cent of men – had a waist circumference that put them at increased risk. Department of Health and Human Services data shows around 60 per cent of Victorian women are overweight or obese (and around three-quarters of men), and about the same proportion of men and women are obese.

“[Being obese] can affect all stages of pregnancy and the postpartum period,” De Luca said. “These women are at much higher rates of developing diabetes, have a high incidence of hypertension and pre-eclampsia and are also at risk of having babies with abnormalities.”

Obesity can increase the risk of babies having spina bifida, linked with gestational diabetes, or of babies being born smaller or of stillbirth, “particularly as you get closer to the due date”.

Kerryn Cugley, a patient at the Joan Kirner Women’s and Children’s Hospital specialty service, said she had lived as overweight all her life and had developed gestational diabetes in her first pregnancy with daughter Amity. The condition returned in her current pregnancy.

Having the support of speciality staff at the Joan Kirner Hospital service for women with higher BMI, the Diamond Clinic, had given her a better understanding of managing pregnancy diabetes and health.

“I wish I had had that support for my first baby, it’s incredible,” she said. “You don’t feel judged or like you shouldn’t be pregnant because you’re overweight. I’m finding I’m not struggling with this pregnancy mentally as much. Every hospital should have this kind of clinic.”

Dr Sarah Price, director of obstetric services at the Royal Women’s Hospital, said obesity had increased in the general population since the 1980s and about one-third of women presenting for maternity care have a BMI above 30, which is technically defined as obesity.

She said it was positive that research is revealing obesity to have underlying genetic, epigenetic and environmental factors, “which helps de-stigmatise obesity as a condition”.

But she said more access to services was needed for women outside Melbourne, especially younger women developing gestational diabetes in regions with lower access to care.

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