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Management of Women with Obesity in Pregnancy

Published: 19/03/2010

This is a joint guideline from the RCOG and the Centre for Maternal and Child Enquiries (CMACE).

Maternal obesity has become one of the most commonly occurring risk factors in obstetric practice. Obesity in pregnancy is usually defined as a body mass index (BMI) of 30 kg/m2 or more at the first antenatal consultation. BMI is a simple index of weight-for-height and is calculated by dividing a person’s weight in kilograms by the square of their height in metres (kg/m2).

There are three different classes of obesity, which recognise the continuous relationship between BMI and morbidity and mortality:

  • BMI 30.0–34.9 (Class I)
  • BMI 35.0–39.9 (Class 2)
  • BMI 40 and over (Class 3 or morbid obesity)

The recommendations in this guideline cover interventions prior to conception and during and after pregnancy. While the majority of the recommendations pertain to women with a BMI ≥30, some recommendations are specific to women in the higher classes of obesity only. Obese women with a BMI below the threshold specified may also benefit from the particular recommendation; however, the chosen BMI cut-offs reflect careful consideration given to the balance of medical intervention versus risk, differences in local prevalence of maternal obesity, and resource implications for local healthcare organisations.

Local maternity services may wish to implement these standards for all women with maternal obesity after consideration of these issues.