Pregnant women who have a body mass index (BMI) that is too high or too low are at an increased risk of suffering complications, requiring more hospital care, a new study indicates.

BMI is a means of assessing whether your weight may be posing a risk to your health. It is calculated using a person's weight and height.

Scottish scientists analysed the records of almost 110,000 pregnant women. The women were divided into five BMI groups:
-A BMI of less than 18.5 was considered underweight
-18.5-24.9 was normal
-25-29.9 was overweight
-30-35 was obese
-More than 35 was severely obese.

The study found that the risk of maternal complications increased in line with BMI. In other words, the heavier a woman was, the more likely she was to suffer complications.

For example, severely obese women were three times more likely to develop gestational diabetes and/or high blood pressure than normal weight women.

Furthermore, the number of hospital admissions required after the birth of their babies was higher among those with a BMI that was too high or too low, compared to those with a normal BMI.

These women also spent longer in hospital.

Underweight women had an 8% increased risk of being admitted to hospital, while overweight women had a 16% increased risk. However, among obese women, this figure rose to 45% and among severely obese women, it hit 88%.

As a result, healthcare costs tended to be higher among these women.

"Our data demonstrates that both high and low maternal BMI are associated with increased risk of complications during pregnancy, increased numbers and duration of maternal admissions and higher health service costs.

"These findings further highlight the need for local and national government in Scotland, and other developed countries, to implement fundamental strategies that will help reduce the prevalence of obesity," the scientists said.

Details of these findings are published in BJOG: An International Journal of Obstetrics and Gynaecology.

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