Gestational diabetes hotspots have expanded across the City of Casey and into Greater Dandenong over successive reporting periods, according to Monash University research.
New data shows high-rate areas moving north within Casey and emerging across parts of Greater Dandenong.
The study, published in BMJ Open and led by PhD candidate Wubet Worku Takele and Associate Professor Jacqueline Boyle from the Eastern Health Clinical School, examined data from more than 1.7 million women who gave birth over six years from 2016 to 2021 across Australia.
The finding reported persistent high-rate areas in Melbourne’s south east, and identified the area’s new hotspots that emerged after 2018, including those in the City of Casey and Greater Dandenong.
Analysis of suburb-level data from 2016–17, 2018–19 and 2020–21 shows that areas once concentrated in Casey South, including Cranbourne, Cranbourne East and Hampton Park–Lynbrook, have broadened into Casey North and later into parts of Greater Dandenong.
In 2016–17, elevated rates were largely confined to Casey South.
By 2018–19, suburbs including Doveton, Hallam, Endeavour Hills and Narre Warren in northern Casey recorded higher rates alongside emerging high-rate areas in Dandenong and Springvale.
By 2020–21, hotspots were evident across most of Casey and Greater Dandenong, with Cranbourne recording 38.7 incidents per 100 women who gave birth, and Dandenong North reaching 33.9, among the highest in the region.
Correspondingly, the number of gestational diabetes hotspots across Casey and Greater Dandenong increased markedly over successive reporting periods.
In 2016–17, just eight suburbs, all within Casey, were identified as hotspots.
That figure rose to 21 by 2018–19 as high-rate areas expanded into Casey North and emerged in Greater Dandenong, before climbing further to 25 suburbs by 2020–21.
In contrast, inner south east Melbourne was among the cold spot areas with lower rates of the disease.
Mr Takele said there are likely many reasons behind the hotspots, ranging from individual to environmental risk factors.
“In most cases, clustering of gestational diabetes overlaps with socioeconomically disadvantaged areas and areas with high segregation of non-European migrant women, known to have an increased risk of diabetes because of genetic, cultural and structural factors,” he said.
He added that other environmental factors, such as limited access to healthy food outlets and high air pollution exposure, may contribute to an increased risk of gestational diabetes, especially in underserved communities.
“Other reasons may relate to a lack of culturally responsive health promotion resources and health services for diverse populations,” he said.
City of Casey and Greater Dandenong are among Melbourne’s fastest-growing and most culturally diverse municipalities, with higher-than-average socioeconomic disadvantage in some suburbs and large populations born overseas, particularly from South and South East Asia.
According to the study, many hotspot areas across Australia had a higher proportion of women born overseas, particularly from South Asia, South-East Asia, Central Asia, the Middle East and Africa.
These groups are known to have a higher biological risk of gestational diabetes, influenced by genetics, metabolic responses, family history and the impact of dietary and lifestyle changes after migration.
In some Melbourne hotspot regions, up to 80 per cent of women diagnosed with gestational diabetes were born overseas.
Another major contributor identified was higher rates of overweight and obesity among women of childbearing age in hotspot areas.
The study points to national data showing that many persistent hotspot regions, including parts of south east Melbourne, also had very high proportions of adult women with obesity, with some areas recording rates of around 70 per cent.
The study also suggests that local environments may also play a role.
Researchers point to evidence from other countries showing that neighbourhood features such as walkability, access to recreation facilities, and healthy food outlets can influence gestational diabetes risk, independent of income or education.
But they note that some areas classified as socioeconomically advantaged still recorded persistent hotspots, suggesting unmeasured environmental factors may also be contributing.
Gestational diabetes is a form of diabetes first diagnosed during pregnancy, where blood glucose levels become higher than normal.
More than 280,000 women give birth in Australia each year, and gestational diabetes, or diabetes that arises during pregnancy, affects nearly one in five pregnancies.
According to Associate Professor Boyle, the diagnosis and treatment of gestational diabetes is important to reduce the risk of complications such as macrosomia (larger than average foetus), labour induction, and birth asphyxia that can lead to complications requiring caesarean delivery.
“Women with gestational diabetes also have an increased risk of developing type 2 diabetes, cardiovascular diseases, and gestational diabetes in the subsequent pregnancy,” she said.
While it has been known that gestational diabetes is increasing in Australia (in 2021-22, 19.3 per cent of pregnant women were diagnosed with the condition, up from 15.1 per cent in 2016-17), the Monash study is the first one to identify those small areas in Australia where the condition is disproportionately higher than others.
According to Associate Professor Boyle, newborns of women with gestational diabetes are more likely to develop metabolic syndrome later in their lives, setting up intergenerational metabolic disorders such as type 1 diabetes.
Co-author Dr Lachlan Dalli from the School of Clinical Sciences at Monash Health said that while further investigation is needed on the interplay between individual-level and environmental-level risk factors for gestational diabetes, the evidence from this study suggests geographically targeted interventions may be required.
“The findings from this study highlight areas where enhanced access to postpartum screening may be needed to mitigate associated complications and downstream chronic conditions, such as type 2 diabetes and cardiovascular disease,” he said.
To read the study: pubmed.ncbi.nlm.nih.gov/41161827/
