Authors' objectives: Physical inactivity and suboptimal diet in pregnancy are important modifiable risk factors for gestational diabetes, a major contributor to pregnancy complications. We aimed to assess the effects of physical activity and/or diet-based lifestyle interventions during pregnancy on gestational diabetes and if these vary by maternal (body mass index, age, parity, ethnicity, education) and intervention characteristics using individual participant data meta-analysis of randomised trials, and a cost-effectiveness analysis. Gestational diabetes mellitus (GDM) is associated with adverse outcomes for both mothers and babies, and drives rising healthcare costs. Behaviour change interventions such as physical activity and diet could prevent GDM. Any variation in the effect across subgroups of women has implications for clinical management and care provision. Despite many trials and aggregate meta-analyses on the effects of lifestyle interventions, the findings were limited due to varied reporting of aggregate data. To address these limitations, we conducted an individual participant data (IPD) meta-analysis of randomised trials to assess the overall and differential effects of lifestyle interventions (physical activity-based, diet-based, mixed) in preventing GDM and its complications, ranked them by effectiveness, and assessed their cost-effectiveness. Primary To evaluate the effects of lifestyle interventions in pregnancy, across all interventions, and for each type of intervention (physical activity-based, diet-based, and mixed) on gestational diabetes as defined by (1) any criteria and by (2) the National Institute for Health and Care Excellence (NICE). To assess if the effects of lifestyle interventions on GDM vary by maternal characteristics [body mass index (BMI) at booking, age, parity, ethnicity and socioeconomic status].

Authors' results and conclusions: Ninety-two trials (32,284 women) were included; 54 (23,698 women) provided individual participant data. Lifestyle interventions reduced the odds of gestational diabetes (any criteria) by 10% in individual participant data trials (odds ratio 0.90, 95% confidence interval 0.80 to 1.02, 54 studies, 23,361 women), and the findings reached statistical significance when non-individual participant data were included (odds ratio 0.81, 95% confidence interval 0.73 to 0.89, 92 studies, 31,947 women). Physical activity significantly reduced the odds of gestational diabetes by 36% (odds ratio 0.64; 95% confidence interval 0.48 to 0.84), and diet by 19% (odds ratio 0.81; 0.69 to 0.96), but not mixed interventions. Women with middle (odds ratio 0.68, 95% confidence interval 0.51 to 0.90) and high educational level (odds ratio 0.71, 95% confidence interval 0.54 to 0.93) benefited more than those with low educational status, and no differences by maternal body mass index, age, parity or ethnicity. There was no significant reduction in gestational diabetes defined by National Institute for Health and Care Excellence criteria (odds ratio 0.98, 95% confidence interval 0.84 to 1.13) in individual participant data trials. For gestational diabetes defined using International Association of Diabetes in Pregnancy Study Group criteria, interventions reduced gestational diabetes by 14% (odds ratio 0.86, 95% confidence interval 0.75 to 0.97, τ2 = 0.00, 16 studies, 6174 women) in individual participant data trials and by 17% (odds ratio 0.83, 95% confidence interval 0.72 to 0.95, τ2 = 0.01, 25 studies, 7883 women) when non-individual participant data trials were added. Overall, physical activity reduced caesarean section (odds ratio 0.83; 0.72 to 0.96), small-for-gestational age (odds ratio 0.72; 0.56 to 0.92) and large-for-gestational age babies (odds ratio 0.81; 0.71 to 0.94); diet-based interventions reduced any preterm birth (odds ratio 0.37; 0.20 to 0.68) compared to controls. No differences were observed for other outcomes. Lifestyle interventions were on average more expensive and more effective at averted gestational diabetes and major outcome averted compared to usual care. Lifestyle interventions in pregnancy prevent gestational diabetes, and the effects vary according to the definition of gestational diabetes. Physical activity-based interventions may be the most effective. Of the 92 eligible studies (32,284 women), 54 trials (23,698 women) contributed data to the IPD meta-analysis. Effects of interventions on gestational diabetes (any criteria) Overall lifestyle interventions compared to usual care, reduced the odds of GDM by 10% on average (OR 0.90, 95 CI 0.80 to 1.02, τ2 = 0.04, 54 studies, 23,361 women) in IPD trials, and by 19% (OR 0.81, 95% CI 0.73 to 0.89, τ2 = 0.07, 92 studies, 31,947 women) when all available aggregate data (38 studies, 8586 women) from studies that did not share IPD were added. Physical activity-based interventions were associated with a 36% lower odds of GDM (OR 0.64, 95% CI 0.48 to 0.84, τ2 = 0.04, 18 studies, 4435 women), and diet-based interventions showed a 19% reduction (OR 0.81; 0.69 to 0.96, τ2 = 0.00, 8 studies, 2974 women) in odds of GDM compared to the control group. There was no reduction in the odds of GDM for studies with mixed interventions (OR 1.05, 95% CI 0.91 to 1.21, τ2 = 0.02, 28 studies, 15,952 women). When aggregate data from studies that did not share IPD were added to the IPD meta-analyses for each intervention type, the results remained statistically significant for both physical activity (OR 0.63, 95% CI 0.53 to 0.75, τ2 = 0.02, 33 studies, 8347 women) and diet-based interventions (OR 0.77, 95% CI 0.60 to 0.98, τ2 = 0.00, 11 studies, 3384 women). We did not find a statistically significant reduction in the odds of GDM for mixed interventions (OR 0.92, 95% CI 0.82 to 1.04, τ2 = 0.05, 48 studies, 20,216 women). When the analysis was limited to IPD studies at low risk of, we observed a non-significant reduction with overall lifestyle interventions (OR 0.94, 95% CI 0.82 to 1.08, τ2 = 0.03, 33 studies, 15,547 women). The findings were statistically significant for physical activity-based interventions (OR 0.59, 95% CI 0.43 to 0.82, τ2 = 0.00, 11 studies, 2993 women), but not for diet-based (OR 0.89, 95% CI 0.69 to 1.16, τ2 = 0.00, 5 studies, 1930 women) or mixed interventions (OR 1.14, 95% CI 1.01 to 1.29, τ2 = 0.00, 17 studies, 10,624 women). Lifestyle interventions reduce the risk of GDM defined by any criteria and IADPSG criteria, but not NICE criteria. The benefits appear to be greater in women with middle and high education level than lower level. Among the intervention types, physical activity appears to be the most effective in preventing GDM. Individual interventions may have some benefits in preventing pregnancy complications like caesarean section, small-for-gestational age, large-for gestational age babies and preterm birth. Overall lifestyle intervention in pregnancy was more cost-effective in women with obesity.

Authors' recommendations: Further exploration of systemic, behavioural and social factors is needed to implement the intervention. The impact of interventions in pregnancy on long-term offspring and maternal (e.g. type 2 diabetes and cardiovascular diseases) outcomes needs evaluation.

Authors' methods: International Weight Management in Pregnancy Collaborative Network database was updated by searching major databases from February 2017 to March 2022. The main outcomes were gestational diabetes by any criteria and by the National Institute for Health and Care Excellence. Other outcomes were gestational diabetes as per International Association of Diabetes in Pregnancy Study Group and maternal and perinatal outcomes. We performed a two-stage random-effects individual participant data meta-analysis to obtain summary estimates (odds ratio) with 95% confidence intervals. Study quality of included trials was assessed, and heterogeneity summarised using τ2. Where possible, we added the aggregate data from non-individual participant data trials to the meta-analysis. We ranked interventions by effectiveness using network meta-analysis and undertook model-based economic evaluation to assess cost-effectiveness. The cost-effectiveness analysis took an NHS cost perspective compared an overall lifestyle intervention versus usual care with a time horizon covering the beginning of pregnancy until the discharge of the mother and infant from the hospital following delivery. We could not identify the specific intervention components and delivery methods associated with improved outcomes, due to variations in reporting. We undertook IPD meta-analysis using a prospective protocol in line with existing recommendations and used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for IPD meta-analysis in reporting our work. The International Weight Management in Pregnancy Collaborative (i-WIP) Network has the largest database of IPD from randomised trials on physical activity and diet in pregnancy identified through a systematic literature search. We updated our current search on MEDLINE, EMBASE, Bioscience Information Service, Latin American and Caribbean Health Sciences Literature, PASCAL, Science Citation Index, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects and Health Technology Assessment Database to identify relevant trials up to March 2022 without language restrictions. Randomised trials that assessed the effects of diet, physical activity or a mixed-approach intervention in pregnancy were included. Mixed approach provided overall guidance on both physical activity and diet-based interventions, with varying levels of intensity and structure. Trials including women with GDM at baseline were excluded. Primary researchers were invited to join the i-WIP Network and share their IPD. The primary outcomes were GDM as defined by any established criteria and by NICE. We performed a two-stage random-effects IPD meta-analysis for all interventions analysed together, and by each intervention type (physical activity-based, diet-based, and mixed approach) to obtain summary intervention effects on GDM using odds ratios (ORs) with 95% confidence intervals (CIs) and summary treatment–covariate interactions. We summarised heterogeneity using τ2 and 95% prediction intervals (PIs). Quality assessment of each trial was assessed using the Cochrane Risk of Bias tool. Publication and availability bias were also assessed by examining small study effects. We categorise interventions by core components and ranked their effectiveness using network meta-analysis, and quantified the differences in fasting and 2-hour post-prandial glucose levels between the groups. A model-based economic analysis was done to assess the cost-effectiveness of the interventions to prevent GDM and its complications compared with usual care.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hta/NIHR129715

Year Published: 2026

URL for published report: https://www.journalslibrary.nihr.ac.uk/hta/GJST1327

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/GJST1327

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk