Pregnant women who are overweight or obese are at an increased risk of experiencing problems during their pregnancy and are therefore more likely to require specialist care, a new Irish study has shown.

Their babies are also more likely to have problems.

Researchers from Queen's University in Belfast and the Belfast Health and Social Care Trust set out to assess the impact of body mass index (BMI) on maternal and neonatal outcomes in over 30,200 pregnancies over an eight-year period.

The women were divided into six groups depending on their BMI - underweight, normal weight, overweight and then three categories of obesity. These were obese class one, two and three, with three being the heaviest.

Among the participants, just over half were a normal weight, at least one in four were overweight and one in 10 were in the obese class one category. Almost 4% were obese class two, while just under 2% were obese class three.

The researchers found that women in the obese class three category were four times more likely to develop the pregnancy complication, gestational diabetes, compared to women of a normal weight.

Women in this category were also more likely to experience a premature delivery and have a baby who needed to be admitted to intensive care.

They were also three times more likely to have a stillbirth.

However, the risks did not just affect the most obese. Those who were overweight and in the ‘lighter' obese groups were at an increased risk of suffering postnatal problems, such as unsuccessful breastfeeding.

At the other end of the spectrum, underweight women were at an increased risk of developing anaemia and were more likely to have a baby with a low birth weight compared to women of a normal weight.

According to the study's co-author, Dr Valerie Holmes of Queen's University, this large study ‘clearly demonstrates that being overweight or obese during pregnancy increases the risk of adverse maternal and neonatal outcomes'.

"By having obesity in sub-classifications, we were able to highlight the relationship between increasing BMI and the increasing risk of adverse outcomes, with women most at risk in obese class three requiring specialist medical care during pregnancy," she explained.

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

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