Obese or underweight pregnant women are at a small but significant increased risk of complications including death, a US study has found.
Researchers at the University of British Columbia in Canada examined health data collected on 743,000 pregnant women between 2004 to 2013 to determine if pre-pregnancy BMI (body mass index) was associated with severe maternal morbidity.
The study, published in journal JAMA, found conditions such as sepsis or acute kidney failure were more common for women who had high or low BMI before conception, and the risk got greater as the BMI increased.
Their risk of dying was also greater. Obese women with a BMI of 40 or greater were at 61 per cent increased risk of maternal mortality, while underweight women - a BMI less than 18.5 - were at a 28 per cent increased risk of dying from complications compared to women with a normal BMI (18.5 to 24.9).
"Among pregnant women in Washington State, unhealthy pre-pregnancy BMI, compared with normal BMI, was associated with a small absolute increase in severe maternal morbidity or mortality," the authors concluded.
Obstetrician Dr Gino Pecoraro - the Federal Australian Medical Association Spokesperson for Obstetrics and Gynaecology - says this large study provides even more compelling reasons for women planning a pregnancy to ensure they are in the normal weight range.
"Underweight women were 1.2 times more likely to suffer significant complications while overweight women showed a steady weight-related increase in risk up to 1.4 times that of their normal weight counterparts," said Dr Pecoraro.
"While the study was undertaken in the US, Australian figures are likely to be similar and there is no reason to expect the experience in our country to be different," he said.
However he did note that the observational study only found an association and was not able to say that the increased weight caused the problems.
The Absolute Risks of Severe Maternal Illness or Death for Unhealthy BMI
* 28.8 more per 10,000 for underweight women with BMI of less than 18.5;
* 17.6 more for overweight women with a BMI of 25.0-29.9;
* 24.9 more for obese women with a BMI of 30.0-34.9;
* 35.8 more for obese women with a BMI of 35.0-39.9;
* 61.1 more for obese women with a BMI of 40 or greater.
