WA's specialist maternity hospital has been forced to widen doorways and upsize theatre equipment to cope with more overweight pregnant women - including some in the extreme "super-obese" category.
Almost one in five pregnant women treated at King Edward Memorial Hospital last year were significantly obese, including some with a body mass index of more than 50.
Figures show that 1028 obstetrics patients with a BMI of 35 and over were booked in last year.
The trend has continued this year, with 811 women with a BMI of 35 and over treated up until last month.
The number of cases has prompted the hospital to enlarge rooms and equipment, including wider doorways, theatre table extenders, reinforced stirrups, scales that can weigh patients up to 300kg and floor-mounted rather than wall-mounted toilets.
Ceiling hoists and air-assisted transfer mats are increasingly being used to protect staff from strain injuries when moving so-called bariatric patients.
BMI, a ratio of weight to height, is considered a strong indicator of the risk of medical complications in the mother and baby during labour and birth.
A BMI of 35 and over requires specialist maternity care, while only KEMH can handle pregnant women with a BMI of more than 40.
A national maternity report this week found that at least 200 WA women who gave birth in 2011 had a BMI of 40 and over, including more than 20 in the "super-obese" category.
Australian Medical Association WA vice-president and obstetrician Michael Gannon said it was a growing and worrying trend.
"These women need careful monitoring in specialist units that have access to high dependency and intensive care units," he said.
"It's a huge issue and we're hoping it will start to plateau soon because it has big implications for the level of care needed for both the mother and baby.
"Unfortunately, obesity is a society-wide issue and most of these women are already obese well before they become pregnant."
Dr Gannon said the risks for obese women trying to have children were wideranging, including infertility issues, gestational diabetes and high blood pressure. It was also more difficult to accurately scan obese women during their pregnancy.