The obesity epidemic is fuelling a worrying trend of grossly overweight pregnant women at WA's specialist maternity hospital, with some weighing more than 200kg.
Doctors and midwives at King Edward Memorial Hospital are seeing a growing number of women in early pregnancy with a body mass index of more than 40, some more than 50. A healthy BMI is 18.5 to 25.
They say it is putting hospitals under increased pressure to provide the highly specialised care needed, as well as putting the lives of women and their babies at risk from complications such high blood pressure and miscarriage.
Women who book in with a BMI over 30, which is considered obese, make up almost a third of those giving birth at KEMH.
Midwifery and nursing director Margaret Davies said most suburban maternity units were equipped to deal with pregnant women with a BMI of up to 30-35, while Joondalup Health Campus could take women with a BMI of up to 40. Bigger women were referred to KEMH.
She said the BMI was calculated soon after women found they were pregnant, in the first trimester.
"These are women who even before they get pregnant have a weight that is quite high, often already over a BMI of 35," she said.
"And now we're seeing a higher proportion of women who have a very high BMI, over 40 and sometimes over 50.
"There are women who come here who have a weight of anything from 150kg up to 200kg, and we've even had some women over 200kg."
Ms Davies said many of peripheral hospitals did not have the equipment or specialist staff to deal with very obese women, particularly in after-hour emergencies.
They did not have beds like those installed at KEMH which could take up weight up to 240kg.
"It can also be difficult to intubate these patients if they need an emergency anaesthetic, and it's often very difficult to give epidurals because of the body mass," she said.
"Their babies tend to be small for their gestational age so there are implications for foetal monitoring. The bigger the woman, the harder it is to monitor the baby before the delivery and during labour."
Ms Davies said there was an increased risk of miscarriage in babies of obese mothers and it was difficult to assess them in the womb because of the mother's size.
Dietitians tried to give obese expectant mothers advice to avoid them putting on a lot of weight during the pregnancy.