A Mediterranean-style diet in pregnant women may decrease the risk for gestational diabetes and reduce gestational weight gain, according to study results published in PLOS Medicine. However, the popular diet did not reduce the overall risk for adverse maternal or offspring complications.

In the ESTEEM study (Effect of Simple, Targeted Diet in Pregnant Women With Metabolic Risk Factors on Pregnancy Outcomes; ClinicalTrials.gov Identifier: NCT02218931), the goal was to assess the effects of a Mediterranean-style diet during pregnancy on maternal and offspring outcomes.

The multicenter randomized controlled study recruited pregnant women aged ≥16 years at <18 weeks’ gestation with a singleton pregnancy from 5 maternity units in the United Kingdom between September 2014 and February 2016. Women with metabolic risk factors (obesity, chronic hypertension, or hypertriglyceridemia) were randomly assigned to usual care or a Mediterranean-style diet, which included high intake of nuts, extra virgin olive oil, fruits, vegetables, unrefined grains, and legumes; moderate to high intake 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.

The primary outcomes were composite maternal end points (gestational diabetes or preeclampsia) and composite offspring end points (stillbirth, small for gestational age, or admission to neonatal care unit).

Of 7950 women screened, the study enrolled 1252 women with metabolic risk factors to an intervention (627 participants) or a control group (625 participants). Complete follow-up was available for 553 and 585 patients in these groups, respectively.

Pregnant women in the intervention group significantly increased their intake of key elements of the Mediterranean diet. As for the primary outcome of the study, the results showed no statistically significant decrease in mother and offspring complications with the Mediterranean-style diet during pregnancy. However, regarding the individual components of the maternal composite outcome, risk for gestational diabetes decreased significantly with the intervention diet (adjusted odds ratio, 0.65; 95% CI, 0.47-0.91; P =.01), but there was no significant effect on preeclampsia. There was also no statistically significant reduction in any individual components of the offspring outcome.

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Women in the intervention group gained less weight in pregnancy compared with the control group (mean gestational weight gain of 6.8 vs 8.3 kg, respectively; mean difference, -1.2 kg; P =.03). Other maternal or offspring secondary outcomes were not significantly different between the groups.

Finally, the researchers completed a literature review and pooled data from the ESTEEM trial with those of a similar randomized trial. The pooled effect estimate (2 trials, 2012 women) revealed a consistent reduction in gestational diabetes (odds ratio, 0.67; 95% CI, 0.53-0.84) with a Mediterranean diet.

“Mediterranean-style diet in pregnancy did not improve the overall maternal and offspring outcomes but has the potential to prevent gestational diabetes,” concluded the researchers, adding that 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.”

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Reference

Al Wattar BH, Dodds J, Placzek A, et al. Mediterranean-style diet in pregnant women with metabolic risk factors (ESTEEM): a pragmatic multicentre randomised trial [published online July 23, 2019]. PLoS Med. doi:10.1371/journal.pmed.1002857