This is a plain English summary of an original research article
Diet and exercise are effective ways of preventing the development of diabetes during pregnancy, known as gestational diabetes.
Gestational diabetes is becoming more common and is associated with poorer outcomes for mother and baby. Diet, physical activity and weight are modifiable risk factors, but trials published to date have shown inconsistent results.
This systematic review pooled 47 trials and found that any form of lifestyle intervention reduced the risk of gestational diabetes by 23%, with similar effects for diet, exercise or both. Interventions were most successful when targeted at high-risk populations, though body mass index alone was not associated with an effect.
As the authors suggest, comprehensive risk assessments that consider body mass index alongside other risk factors may help to identify women who could benefit most from structured lifestyle interventions during pregnancy.
Why was this study needed?
Gestational diabetes is associated with various adverse outcomes for mother and baby. Women with the condition are at higher risk of having their labour induced, having a caesarean section, developing pre-eclampsia, or developing type 2 diabetes after pregnancy. Babies born to mothers with gestational diabetes tend to be larger. They are at higher risk of experiencing a difficult labour, and needing additional care in the neonatal unit, and are at risk of developing cardiovascular and metabolic disease in the future.
A recent systematic review finds that prevalence estimates for gestational diabetes have risen since 2010, with the condition now reported to affect between 8 and 24% of pregnant women in the UK. The rising prevalence of gestational diabetes combined with adverse outcomes that have a long-lasting impact, emphasise the need for prevention as well as management.
What did this study do?
This systematic review included 47 randomised controlled trials involving 15,745 women. It looked at the effectiveness of lifestyle interventions for preventing gestational diabetes.
Studies were international, with one trial from the UK. Nineteen studies evaluated the effect of exercise, 11 examined diet, and 17 studies examined both. Interventions started from 7 to 20 weeks gestation. Most studies recruited overweight or obese women. Various diagnostic criteria were used to define gestational diabetes. Subgroup analyses examined the moderating effect of study methods, interventions and participant characteristics.
Study quality was variable, with selective or incomplete reporting being the most likely sources of bias. Intervention adherence also varied, which demonstrates the difficulty in implementing lifestyle interventions in real life.
What did it find?
- Compared with standard care, any lifestyle intervention during pregnancy involving diet, exercise or both reduced risk of gestational diabetes by 23% (relative risk [RR] 0.77, 95% confidence interval [CI] 0.69 to 0.87; 47 trials). There was moderate difference (heterogeneity) in the results of individual trials.
- There was little difference in the effect of different interventions. Exercise interventions reduced risk by 30% (RR 0.70, 95% CI 0.59 to 0.84; 19 trials), dietary interventions reduced risk by 25% (RR 0.75, 95% CI 0.59 to 0.95; 11 trials), and mixed interventions gave a less precise 14% reduction in risk of gestational diabetes (RR 0.86, 95% CI 0.71 to 1.04; 18 trials).
- Interventions were most effective in populations with higher rates of gestational diabetes. In a population with 20% prevalence, interventions such as moderate intensity exercise for 50-60 minutes twice a week could reduce risk by 20%. This means that four cases of gestational diabetes could be avoided if interventions were provided to 100 women.
- BMI was not associated with intervention effectiveness and as such was not a sufficient indicator of high risk, alone. However, ethnicity was an influential factor, with interventions in women of Asian, African or Latin American origin demonstrating greater success.
- Overall four key aspects or ‘factors’ were identified that could improve the effectiveness of interventions: screening and targeting high-risk populations using a comprehensive risk evaluation model; early initiation of the intervention; adequate intensity and frequency of exercise; and weight gain management during pregnancy.
What does current guidance say on this issue?
The 2015 NICE guideline on diabetes in pregnancy lists obesity, prior gestational diabetes, previous large baby, family history of diabetes, or ethnic predisposition as risk factors for gestational diabetes. Following diagnosis, NICE advises that women are informed of the benefits of diet and exercise, and possibly medication.
The International Federation of Gynaecology and Obstetrics Initiative on gestational diabetes similarly recognises that nutrition counselling and physical activity are the primary tools for management. Neither guideline specifically mentions diet or physical exercise as ways to reduce the risk of gestational diabetes, as a preventative measure.
What are the implications?
This is reportedly the first review to quantify the size of effect that diet and exercise interventions can have on preventing gestational diabetes. It also lends supports to current recommendations to identify and target those at high risk by considering factors such as ethnicity, BMI, medical or family history.
Current practice may often involve at-risk women being given general lifestyle advice around diet and activity rather than supported interventions. Further studies may be required to add to the evidence and provide more insightful information around the structure and content of preventive interventions in order to maximise impact of existing guidelines.
Citation and Funding
Guo XY, Shu J, Fu XH et al. Improving the effectiveness of lifestyle interventions for gestational diabetes prevention: a meta‐analysis and meta‐regression. BJOG. 2018; Sep 14. doi: 10.1111/1471-0528.15467. [E-pub ahead of print].
This study was supported by the National Basic Research Programme of China, the National Natural Science Foundation of China, the NSFC-CIHR Joint Health Research Programme, the Natural Science Foundation of Zhejiang Province, and the Medicine and Health Clinical Research Programme of Zhejiang Province.
Farrar D, Simmonds M, Griffin S et al. The identification and treatment of women with hyperglycaemia in pregnancy: an analysis of individual participant data, systematic reviews, meta-analyses and an economic evaluation. Health Technol Assess. 2016;20(86).
Hod M, Kapur A, Sacks DA et al. The International Federation of Gynecology and Obstetrics (FIGO) Initiative on gestational diabetes mellitus: a pragmatic guide for diagnosis, management, and care. Int J Gynaecol Obstet. 2015;131(Suppl 3):S173-211.
NICE. Diabetes in pregnancy: management from preconception to the postnatal period. NG3. London: National Institute for Health and Care Excellence. 2015.
RCOG. Gestational diabetes. London: Royal College of Obstetricians and Gynaecologists; 2013.
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