A simple Mediterranean-style diet in pregnancy does not reduce the overall risk of adverse maternal and offspring complications, but has the potential to reduce weight gain in pregnancy and the risk of gestational diabetes, according to results of a new clinical trial.

The trial involved 1,252 women at five UK maternity units – four in London including St George’s University Hospitals NHS Foundation Trust and Barts Health NHS Trust and one in Birmingham.

The results, published in the journal PLOS Medicine, show that having a Mediterranean-style diet (including 30g of mixed nuts per day and extra virgin olive oil) led to a 35 per cent lower risk of developing diabetes in pregnancy, and on average 1.25kg less weight gain in pregnancy, compared to those who received routine antenatal care.

The study, led by Queen Mary University of London and the University of Warwick, suggests a Mediterranean-style diet could be an effective intervention for women who enter pregnancy with pre-existing obesity, chronic hypertension or raised lipid levels.

Professor Asma Khalil, Consultant Obstetrician and Lead Investigator of the study at St George’s, said: “We are very proud to have been one of the trial centres contributing to such an important study. Pregnancy is a golden opportunity for health interventions, such as improving our diet. Weight gain and diabetes contribute to many health problems and the fact that we found an easy, safe and effective intervention to reduce the risk in pregnancy is to be celebrated.”

Professor Shakila Thangaratinam from Queen Mary University of London said: “This is the first study to show that pregnant women at high risk of complications may benefit from a Mediterranean-style diet to reduce their weight gain and risk of gestational diabetes.

“Implementing this diet seems to be effective and acceptable to women. Current national dietary guidelines do not include the key components of the Mediterranean-style diet in their recommendations. Women who are at risk of gestational diabetes should be encouraged to take action early on in pregnancy, by consuming more nuts, olive oil, fruit and unrefined grains, while reducing their intake of animal fats and sugar.”

One in four mothers enter pregnancy with pre-existing obesity, chronic hypertension or raised lipid levels. These can lead to pregnancy complications, including gestational diabetes (when high blood sugar develops during pregnancy) and pre-eclampsia – the onset of high blood pressure in pregnancy which can sometimes develop into more serious conditions affecting multiple organs. These mothers and their babies are also at long-term risk of diabetes and cardiovascular complications.

A Mediterranean-style diet, rich in unsaturated fatty acids, reduces the incidence of cardiovascular diseases in the non-pregnant population. In pregnancy, such a diet has the potential to improve maternal and offspring outcomes, but has not been widely evaluated until now.

Multi-ethnic inner-city pregnant women with metabolic risk factors, including obesity and chronic hypertension, were randomised to either receive routine antenatal care or a Mediterranean-style diet in addition to their antenatal care. The diet included a high intake of nuts, extra virgin olive oil, fruit, vegetables, non-refined grains and legumes; moderate to high consumption of fish, small-moderate intake of poultry and dairy products; and low intake of red meat and processed meat; and avoidance of sugary drinks, fast food, and food rich in animal fat.

Despite the improvements in gestational diabetes and pregnancy weight gain, there was no improvement in other important pregnancy complications such as high blood pressure, pre-eclampsia, stillbirth, small for gestational age foetus, or admission to a neonatal care unit.

The participants in the Mediterranean-style diet group reported better overall quality of life than those in the control group and reduced bloatedness in pregnancy, but there was no effect on other symptoms such as nausea, vomiting or indigestion.

When the data from the study was combined with published data from a Spanish study involving 874 pregnant women on a Mediterranean diet, the team observed a similarly large reduction in gestational diabetes (a 33 per cent reduction), but no effect on other outcomes.

Notes to editors

Research paper: https://journals.plos.org/plosmedicine/article/related?id=10.1371/journal.pmed.1002857

More information: https://bartscharity.org.uk/news/new-research-finds-that-a-mediterranean-diet-can-help-pregnant-women/

This study was led by Barts Research Centre for Women’s Health and funded by Barts Charity.

For media enquiries, please contact: 

Pippa Harper, Media Manager at St George’s, via philippa.harper@stgeorges.nhs.uk for St George’s queries.

Joel Winston, Communications Manager at Queen Mary University of London, via j.winston@qmul.ac.uk for overall study queries.