The women who took part in the study followed a Mediterranean-style diet, by eating more nuts, extra virgin olive oil, fish, white meat and pulses; while cutting their levels of red meat, butter, margarine, and cream. Researchers also asked the women to avoid sugary drinks, fast food, and those high in animal fats.

In general, a Mediterranean-style diet is rich in nuts, extra virgin olive oil, fruits, vegetables, non-refined grains, and legumes. It also contains lots of fish, low to moderate levels of poultry and dairy, and small amounts of red and processed meats. Past studies have linked the lifestyle to preventing depression, better sleep, and easing the symptoms of anxiety.

Shakila Thangaratinam of the Barts and the London School of Medicine, Queen Mary University London and colleagues found women who followed this diet were less likely to develop gestational diabetes, a form of the condition which affects around 2 to 10 percent of pregnant women in the U.S. Around half of those go on to develop type 2 diabetes, according to the Centers for Disease Control and Prevention.

Gestational diabetes can lead to complications for expectant mothers, including high blood pressure, while the baby is more likely to be born large, delivered via c-section, or born early.

A total of 1,252 pregnant women being treated across five maternity units in inner-city London or Birmingham in the U.K. took part in the research published in the journal PLOS Medicine.

The women were above the age of 16, and had at least one metabolic risk factor, which meant they had a higher chance of developing complications during pregnancy. The term “metabolic factors” describes those with obesity, high blood pressure, or hypertriglyceridaemia, which is linked to cardiovascular disease. These raise the risk of conditions such as heart disease, diabetes, and stroke. The control group were given standard dietary advice provided to pregnant women in the U.K.

Researchers assigned participants dietary advice at 18, 20, and 28 weeks into their pregnancy. Of the total, 593 followed the diet, while 612 acted as the control group.

The expectant mothers who followed the diet saw their odds of developing gestational diabetes drop by 35 percent. And they gained less weight than the control group, at 6.8 kilograms compared with 8.3 kilograms on average.

However, the diet didn’t seem to affect the mother or offspring’s overall risk of experiencing complications.

The authors argued that future studies should look at whether eating the Mediterranean-style diet can reduce the risk of childhood obesity in babies, as well as allergies, asthma, and the mother’s risk of developing type 2 diabetes.

Professor Alfonso Luis Calle-Pascual of the Health Research Institute of the San Carlos Clinical Hospital who did not work on the study told Newsweek: “This is an important study, which includes women of multiethnic origin and high risk to develop adverse events during pregnancy and receive nutritional treatment based on the principles of the Mediterranean diet compared to the usual diet.”

Speaking broadly he added women and their newborns can find benefits in using extra virgin olive oil as a source of culinary fat exclusively; using at least four tablespoons daily; and consuming a handful of nuts daily instead of other snacks."