Diet and physical activity interventions reduce pregnancy weight gain compared with control, with dietary interventions having the greatest effect
- Correspondence to
: Dr Nicola Heslehurst
Institute for Health & Society, Baddiley-Clark Building, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK;
Commentary on: 
Implications for practice and research
Behavioural interventions can reduce maternal, fetal and neonatal obstetric and weight-related risks.
Good-quality research is required to inform the development of behavioural interventions to determine effectiveness and cost-effectiveness for short-term and long-term health outcomes.
There has been a rapid development of international maternal obesity and gestational weight gain (GWG) guidelines due to increasing evidence of risk.1–3 Maternal obesity has doubled over two decades with significant UK regional variation.4 ,5 The majority of published GWG research is among non-UK populations.2 This systematic review aimed to determine the effectiveness of behavioural interventions in pregnancy at reducing obstetric and weight-related risk.
Randomised controlled trials (RCTs) evaluating dietary, physical activity or mixed behavioural interventions in pregnancy were included. Primary outcomes were maternal and infant weight-related changes. Delphi methods ranked obstetric outcomes for importance by clinicians. Database searches identified 44 eligible RCTs. Two researchers independently screened studies, performed data extraction and quality assessment. Meta-analyses were conducted to determine the effect of dietary, physical activity and combined behavioural interventions on maternal, fetal and neonatal obstetric and weight-related outcomes.
Behavioural interventions significantly reduced risks for some outcomes (varied by intervention type) including GWG, birth weight, gestational diabetes, pre-eclampsia, hypertension, preterm delivery and shoulder dystocia. There were also borderline and non-significant trends towards the reducing risk of large-for-gestational-age, intrauterine death and exceeding the USA Institute of Medicine (IoM) weight gain guidelines. There was no evidence of risk reduction for some outcomes, including small-for-gestational-age, vaginal delivery and postpartum haemorrhage.
Dietary interventions achieved more significant results compared with other interventions. Only physical activity interventions reduced birth weight and risk of exceeding IoM guidelines.
This systematic review was conducted with methodological rigour; however, the data were primarily from low quality and underpowered studies, acknowledged as research limitations. The authors’ interpretation emphasised the benefits of dietary interventions over physical activity or combined interventions. This interpretation neglects to consider the limitations of the data sources. A more balanced interpretation would be that the current evidence base suggests that behavioural interventions can reduce risk, and that dietary approaches are most effective. However, further good quality research is required to determine the most effective approach, especially in light of the potential effect of physical activity on birthweight and maternal weight gain.
Reference is made to the cost effectiveness of dietary versus physical activity interventions in non-pregnant populations. The transferability to pregnant populations is questionable due to different weight-related aims and targeted health outcomes, and could be misleading when commissioning and developing services. A recent economic evaluation reported “considerable uncertainty around all aspects of the economics of weight management in pregnancy” due to the lack of available interventional cost data, limitations in evaluating effectiveness and strong underlying assumptions of health-related benefits.6
The authors recommend that ongoing trials should use the clinician-ranked biomedical effectiveness outcomes, while the targeted weight-related behaviours have strong psychosocial relationships. Outcomes not included, but arguably equally important, are psychological and long-term impacts such as postnatal weight retention as a mediator of obesity development. Pregnant women's perspectives on the importance of outcomes could also have direct implications for their engagement with behavioural interventions, and therefore intervention effectiveness.
The authors identified data on the safety of gestational weight management, predominantly from periods of extreme malnutrition including famine and war. The effects of this nutritional status on fetal development are not comparable with limiting GWG through moderate behaviour change, as the authors acknowledge. While the limited data available suggest that there are no safety concerns for behavioural interventions, further evidence is needed on the safety of moderate pregnancy weight loss.
The review provides promising evidence that obstetric and weight-related outcomes can be improved through behavioural interventions during pregnancy. However, higher quality evidence is needed from adequately powered studies that also examine non-obstetric outcomes, long-term implications and cost effectiveness of pregnancy-specific interventions.