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This large NIHR-funded UK trial found that a behavioural intervention for obese pregnant women did not reduce their risk of developing diabetes during pregnancy, or having a baby born too large for the duration of pregnancy (large-for-dates). However, the intervention did reduce the mothers’ weight gain slightly and increased their physical activity. Women received advice about healthy eating and exercise alongside training in specific behavioural techniques. Hour-long sessions with a health trainer were spread over eight weeks. The techniques taught to women included how to monitor food intake and activity levels themselves, how to solve problems in sticking to the advice and how to enlist help and support to achieve their goals.

All women in this trial had blood sugar testing through their pregnancy and about 25% of women developed diabetes during pregnancy. They then received appropriate treatment. Better treatment of women in the trial, and the use of a newer lower threshold for diagnosing diabetes during pregnancy, may have reduced the proportion of babies born large-for-dates in both arms and so reduced the apparent effectiveness of the intervention. The trial result does emphasise the need to follow NICE recommendations to test for diabetes in all pregnant women with obesity.

Why was this study needed?

Obesity rates in UK women have risen between 1993 and 2011 from 16% to 26%. Rates of gestational diabetes are also increasing. Women who are obese when they become pregnant have a higher risk of developing diabetes, high blood pressure, or having babies that are on average larger than the duration of pregnancy would predict. This can lead to complications around birth, including a need to start labour artificially, use instruments like forceps to help delivery, or deliver the baby via caesarean section. Previous trials have suggested that behavioural interventions might improve health and delivery outcomes for mothers and babies, but trials have usually been too small to measure the impact on conditions like diabetes in pregnancy.

NIHR funded this UK-based trial, called UPBEAT, to find out if behavioural interventions addressing diet and physical activity can reduce the risk of pregnant women with obesity developing diabetes or having large babies.

What did this study do?

This randomised controlled trial included 1,555 obese pregnant women with an average body mass index (BMI) of 36kg/m2 at eight NHS hospitals in large cities in the UK. The women were randomly allocated to receive a behavioural intervention delivered by a health trainer or to a standard pregnancy care group. The behavioural intervention involved weekly one hour sessions over eight weeks and included advice on self-monitoring, problem solving and enlisting social support. Individually tailored advice and information about healthy eating and exercise was also provided. The main outcomes were developing diabetes during pregnancy (tested between 27 and 28 weeks) and having a baby born large-for-dates. This was a large and methodologically robust trial providing reliable evidence.  The adherence to the programme was good, with on average seven out of eight intervention sessions attended by the women.

What did it find?

  • The behavioural intervention had no effect on the risk of diabetes during pregnancy. The proportion of women who developed diabetes was similar in the two groups, 25% in the intervention group and 26% in the standard care group (risk ratio [RR] 0.96, 95% confidence interval [CI] 0.79 to 1.16).
  • The behavioural intervention also had no effect on the proportion of babies born large-for-dates, which was 9% in the intervention group and 8% in the standard care group (RR 1.15, 95% CI 0.83 to 1.59). This incidence is well below the 16% reported in UK women with similar BMI and may be the result of using a new, lower threshold for treating diabetes in this trial.
  • There was no difference in the rate of adverse events between the two groups, including rates of miscarriage, stillbirth or newborn death.
  • The behavioural intervention did improve some study outcomes; it improved the diet and physical activity of the pregnant women and reduced their weight gain slightly (by about 500g on average) during pregnancy.

What does current guidance say on this issue?

The 2010 NICE public health guideline on weight management before, during and after pregnancy provides recommendations for pregnant women categorised as obese, with BMI 30 or more. This includes providing practical and tailored information and advice about the benefits of a healthy diet and physical activity.

This guideline also advises how GPs and other health professionals can help obese women to lose weight after childbirth, including the use of “evidence-based behaviour-change techniques to motivate and support women to lose weight”.

The 2014 NICE guideline on obesity recommends behavioural interventions delivered by trained professionals for all people who are obese, but does not give specific recommendations for pregnant women.

NICE 2015 guidance on diabetes in pregnancy recommends that all obese pregnant women with BMI above 30 receive a glucose tolerance test to test for pregnancy diabetes.

What are the implications?

The UK-based trial found evidence that a complex behavioural intervention was no more effective at reducing the risk of developing diabetes during pregnancy in obese women or having a large-for-dates baby than standard care. However, it did find that the behavioural intervention improved diet slightly and physical activity in pregnant women with obesity. It may be that the results of the smaller trials that did show an effect had underlying bias towards the intervention. Therefore the systematic reviews based on these previous trials should be treated with caution.

The majority of women in this study received diabetes testing during pregnancy, and those diagnosed received appropriate treatment. This, the researchers consider, may have led to a reduction in the proportion of babies being born large-for-dates. This finding reinforces the need to follow the 2015 NICE recommendations to test all women with obesity for diabetes in pregnancy.



Poston L, Bell R, Croker H, et al. Effect of a behavioural intervention in obese pregnant women (the UPBEAT study): a multicentre, randomised controlled trial. Lancet Diabetes Endocrinol. 2015;3: 767–77.

This project was funded by the National Institute for Health Research, Guys and St Thomas’ Charity, Chief Scientist Office Scotland, and Tommy’s Charity.



NHS Choices. Overweight and pregnant. London: Department of Health. 2015.

NICE. Diabetes in pregnancy: management of diabetes and its complications from preconception to the postnatal period. NG3. London: National Institute for Health and Care Excellence; 2015.

NICE. Weight management before, during and after pregnancy. PH27. London: National Institute for Health and Care Excellence; 2010.

NICE. Obesity: identification, assessment and management of overweight and obesity in children, young people and adults. CG189. London: National Institute for Health and Care Excellence; 2014.

RCOG.  Diagnosis and treatment of gestational diabetes (Scientific impact paper no. 23).   London: Royal College of Obstetricians and Gynaecologists; 2011.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre

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Obesity is defined as having a body mass index (BMI) of more than 30kg/m2. The BMI is calculated using a person’s weight and height. It is estimated that around 15-20% of pregnant women in the UK are categorised as obese.  Obesity is associated with a number of complications for pregnant women and their babies, and higher BMI is linked to higher risks. Women with BMI > 30 are three times more likely to develop diabetes in pregnancy.


Expert commentary

Provision of dietary and physical activity advice on top of routine care does not prevent gestational diabetes in obese women. Although women assigned to the intervention compared to the control group gained less weight and were less adipose (sum of skinfolds), these differences were marginal (half a kilo and 3mm respectively) and arguably not clinically relevant.

The health of child bearing age women is not just an issue for pregnancy. The failure of this trial intervention to influence gestational diabetes rates suggests that behavioural change interventions aimed at reducing obesity related gestational diabetes and perhaps other ill-health conditions may be more successful outside of pregnancy when a more sustained approach to healthy living can take place. If we can find ways to stem the rising obesity rate in the general population and help those already overweight/obese achieve a normal weight, health improvements for the pregnant population will follow.

Dr Diane Farrar, NIHR post-doctoral research fellow, Maternal and Child Health, Bradford Institute for Health Research, Bradford Royal Infirmary

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