By: 3 April 2013

Researchers from Norway found that women with a high pre-pregnancy body mass index (BMI) had an increased risk of vacuum extraction delivery or Caesarean section.

Their findings, which appear in the journal Acta Obstetricia et Gynecologica Scandinavica, also investigate the effect of gestational weight-gain on the type of delivery women may need to have.

Obesity is a global health issue, with the World Health Organisation (WHO) reporting that 1.4 billion adults were overweight (BMI of 25-29.9) in 2008 and more than half a billion would be considered obese (BMI of 30 or more). In Norway, previous studies estimate that obesity prevalence among women of reproductive age has increased two- to three-fold in the last generation.

“Our study examines the effect of pre-pregnancy BMI and gestational weight gain on the mothers’ risk of operative delivery,” said Dr Nils-Halvdan Morken, lead author of the study. “With such alarming rates of obesity, understanding its impact is an important health issue, particularly for women in child-bearing years.”

The research team used data taken from participants of the Norwegian Mother and Child Cohort Study (MoBa) – a prospective, population-based group of women giving birth in Norway between 1999 and 2008. A sample of 50,416 women who gave birth to one child was included in the study, and those experiencing preeclampsia, hypertension, diabetes, gestational diabetes or placenta previa were excluded.

Results show that overweight and obese women before pregnancy were at increased risk of C-section. Women with a pre-pregnancy BMI of 40 or more had the strongest risk of C-section and increased risk of vacuum extraction delivery. Researchers also found that women who gained 16kg or more while pregnant significantly increased the risk of forceps, vacuum extraction and C-section – a finding that was independent of BMI prior to pregnancy. Obese women had significantly lower gestational weight gain, but their babies tended to be larger.