Graham A. Hitman, Nilaani Murugesu, Maira Bes-Rastrollo, Richard Hooper, Eleni Spyreli, Lee Beresford, Frances Austin, Khalid S. Khan, Julie Dodds, Francisco Jose Gonzalez Carreras, Amanda P. Moore, Tessa J. Roseboom, Bassel H. Al Wattar, Shakila Thangaratinam, Anna Placzek, ESTEEM study group, APH - Health Behaviors & Chronic Diseases, APH - Aging & Later Life, Obstetrics and Gynaecology, ARD - Amsterdam Reproduction and Development, and Epidemiology and Data Science
Background Pregnant women with metabolic risk factors are at high risk of complications. We aimed to assess whether a Mediterranean-style diet reduces adverse pregnancy outcomes in high-risk women. Methods and findings We conducted a multicentre randomised trial in 5 maternity units (4 in London and 1 in Birmingham) between 12 September 2014 and 29 February 2016. We randomised inner-city pregnant women with metabolic risk factors (obesity, chronic hypertension, or hypertriglyceridaemia) to a Mediterranean-style diet with high intake of nuts, extra virgin olive oil, fruits, vegetables, nonrefined grains, and legumes; moderate to high consumption of fish; low to moderate intake of poultry and dairy products; low intake of red and processed meat; and avoidance of sugary drinks, fast food, and food rich in animal fat versus usual care. Participants received individualised dietary advice at 18, 20, and 28 weeks’ gestation. The primary endpoints were composite maternal (gestational diabetes or preeclampsia) and composite offspring (stillbirth, small for gestational age, or admission to neonatal care unit) outcomes prioritised by a Delphi survey. We used an intention-to-treat (ITT) analysis with multivariable models and identified the stratification variables and prognostic factors a priori. We screened 7,950 and randomised 1,252 women. Baseline data were available for 593 women in the intervention (93.3% follow-up, 553/593) and 612 in the control (95.6% follow-up, 585/612) groups. Over a quarter of randomised women were primigravida (330/1,205; 27%), 60% (729/1,205) were of Black or Asian ethnicity, and 69% (836/1,205) were obese. Women in the intervention arm consumed more nuts (70.1% versus 22.9%; adjusted odds ratio [aOR] 6.8, 95% confidence interval [CI] 4.3–10.6, p ≤ 0.001) and extra virgin olive oil (93.2% versus 49.0%; aOR 32.2, 95% CI 16.0–64.6, p ≤ 0.001) than controls; increased their intake of fish (p < 0.001), white meat (p < 0.001), and pulses (p = 0.05); and reduced their intake of red meat (p < 0.001), butter, margarine, and cream (p < 0.001). There was no significant reduction in the composite maternal (22.8% versus 28.6%; aOR 0.76, 95% CI 0.56–1.03, p = 0.08) or composite offspring (17.3% versus 20.9%; aOR 0.79, 95% CI 0.58–1.08, p = 0.14) outcomes. There was an apparent reduction in the odds of gestational diabetes by 35% (aOR 0.65, 95% CI 0.47–0.91, p = 0.01) but not in other individual components of the composite outcomes. Mothers gained less gestational weight (mean 6.8 versus 8.3 kg; adjusted difference −1.2 Kg, 95% CI −2.2 to −0.2, p = 0.03) with intervention versus control. There was no difference in any of the other maternal and offspring complications between both groups. When we pooled findings from the Effect of Simple, Targeted Diet in Pregnant Women With Metabolic Risk Factors on Pregnancy Outcomes (ESTEEM) trial with similar trials using random effects meta-analysis, we observed a significant reduction in gestational diabetes (odds ratio [OR] 0.67, 95% CI 0.53–0.84, I2 = 0%), with no heterogeneity (2 trials, 2,397 women). The study’s limitations include the use of participant reported tools for adherence to the intervention instead of objective biomarkers. Conclusions A simple, individualised, Mediterranean-style diet in pregnancy did not reduce the overall risk of adverse maternal and offspring complications but has the potential to reduce gestational weight gain and the risk of gestational diabetes. Trial registration ClinicalTrials.gov NCT02218931., Bassel H. Al Wattar and colleagues reveal reduced levels of gestational diabetes for obese pregnant women who adopt a Mediterranean diet., Author summary Why was this study done? A Mediterranean-style diet reduced the risk of type 2 diabetes and cardiovascular complications in randomised trials involving the general population with risk factors. To date, no trial has evaluated the effects of a Mediterranean-style diet in pregnancy on maternal and offspring outcomes. What did the researchers do and find? In the Effect of Simple, Targeted Diet in Pregnant Women With Metabolic Risk Factors on Pregnancy Outcomes (ESTEEM) study, 1,252 pregnant women with metabolic risk factors from 5 inner-city United Kingdom hospitals were randomly allocated to follow a Mediterranean-style diet (supplemented with mixed nuts and extra virgin olive oil) or routine antenatal care, and the overall maternal (gestational diabetes or preeclampsia) and offspring outcomes (small-for-gestational age, stillbirth, or admission to the neonatal care unit) were assessed. Pregnant women allocated to the Mediterranean-style diet increased their intake of key components of this diet and gained on average 1.25 kg less weight than those who had routine care. There were no statistically significant reductions in overall maternal and offspring complications in pregnant women who followed a Mediterranean diet compared with usual care. Of the individual outcomes, the risk of gestational diabetes apparently decreased by 35% with the intervention. A meta-analysis of ESTEEM study results with a similar trial showed a 33% reduction in gestational diabetes but no effect on other outcomes. What do these findings mean? It is feasible to deliver a Mediterranean-style diet to inner-city pregnant women and increase their uptake of relevant dietary components. Mediterranean-style diet in pregnancy did not improve the overall maternal and offspring outcomes but has the potential to prevent gestational diabetes. Future studies should assess the effect of in utero exposure to Mediterranean-style diet—particularly to nuts and olive oil—on childhood obesity, allergy, and asthma.