Introduction

This review evaluated the effects of dietary and lifestyle interventions, including physical activity, on the prevention and reduction of obesity in pregnancy, an important area of public health given the increasing prevalence of obesity. We undertook three distinct but related pieces of work:

1. a systematic review of the evidence to evaluate the effect of dietary and lifestyle interventions on maternal and fetal weight (primary outcome), obstetric outcomes and fetal and neonatal morbidity and mortality
2. a systematic review of the evidence to evaluate the risks of adverse effects in the mother or fetus as a result of interventions in pregnancy
3. grading of the quality of evidence for critical and important outcomes.

This work has been described in detail in the previous sections. This chapter summarises the key findings and limitations of the work undertaken. It draws conclusions and makes recommendations for research.

Main findings

• Interventions to manage weight in pregnancy were effective at reducing weight gain in pregnancy, with dietary interventions being the most effective.
• The commonest diet evaluated in the studies was a balanced calorie regime with low fat or cholesterol and high fibre. Interventions were delivered in both primary and secondary care. Physical activity involved moderate exercise with low-intensity resistance training.
• The small reduction in birthweight appeared to be of benefit by reducing the risk of LGA fetuses. This reduction in birthweight did not show as an increase in the incidence of SGA fetuses.
• Dietary intervention showed benefit in reducing obstetric complications such as preeclampsia, gestational hypertension and preterm delivery compared with other interventions. Dietary intervention also reduced the risks of shoulder dystocia of the fetus. There was no effect on any other fetal and neonatal morbidity and mortality outcomes with any intervention.
• There was no evidence of maternal or fetal harm resulting from the diet and physical activity interventions recommended in current clinical practice.
• Evidence quality for effectiveness outcomes was more often graded moderate or high compared with evidence quality for adverse effects. The quality of evidence for adverse effects for both diet and physical activity was very low.

Strengths of the report

This systematic review comprehensively addressed the benefits and harms of the various weight management interventions in pregnancy. In doing so, compared with other reviews, it identified the largest quantity of evidence, especially RCTs. A Delphi survey of clinicians was the first attempt to rank the outcomes according to their importance. The grading of the strength of evidence for the outcomes prioritised provides the much-needed clarity to make judgements about effects and generate recommendations.

Limitations of the report

• It was not possible to provide effectiveness data for all of the outcomes and subgroups; however, the critical and important outcomes are well covered.
• The interpretation of the findings is limited by the paucity of descriptive information on the intensity and duration of intervention, means of provision, patient compliance and any management that can potentially facilitate or hinder implementation. The estimate of reduced gestational weight gain with diet was associated with significant heterogeneity.
• No studies performed a face-to-face comparison of various interventions, thereby restricting the ranking of interventions based on effectiveness.
• The grading of evidence was often limited by the poverty of reporting. The poor quality of evidence on adverse effects was a particular problem.
• There was no evidence on popular diets such as the ‘high-protein, low-carbohydrate’, ‘no carbohydrate’, Slimming World and Atkins diets.
• There were no relevant data on the quality of life of the participants.

Overall conclusion

Despite the above limitations some clear conclusions can be made. There is benefit from weight management interventions, especially dietary intervention, in reducing weight gain in pregnancy (evidence quality moderate). Interventions reduced the risk of pre-eclampsia and shoulder dystocia (evidence quality low to high). Interventions based on diet are effective in reducing the main obstetric complications such as pre-eclampsia, gestational hypertension and shoulder dystocia (evidence quality moderate to moderate). Weight management interventions reduce the risk of having large babies. There is no evidence of harm to the mother or fetus from the diet or physical activity components of the interventions currently used.

Recommendations for research

These recommendations are guided by gaps identified and the evidence grading:

• If RCTs are undertaken they should focus on clinically relevant outcomes.
• Individual patient data meta-analysis can improve the interpretation of current data.
• The long-term effects of the interventions on the mother and fetus and the safety of the interventions needs further evaluation.
• Engagement with pregnant women can identify the outcomes that they consider relevant to themselves and their babies.
• Cost-effectiveness can be assessed by undertaking a model-based health economic evaluation.
• If weight management interventions are implemented based on current evidence and ongoing studies, service evaluation should include an assessment of uptake, compliance and adverse effects.