 The Mediterranean diet is rich in fruit and vegetables |
The Crete team studied 468 mothers and their children from pregnancy to six and a half years after the birth.
They found asthma and allergies were significantly less common in children whose mothers ate lots of vegetables, fruit, nuts and fish during pregnancy.
The Thorax study also found eating high levels of red meat increased the risk.
It made that conclusion in cases where red meat was being eaten more than three to four times a week.
 |  This is of particular significance to mothers in the UK as we have one of the highest rates of childhood asthma worldwide  Leanne Male Asthma UK |
More than five million people in the UK have asthma, and one in 10 children is affected.
Previous work by the same team, from the University of Crete, found that children who ate a Mediterranean diet appeared to be protected from asthma and allergies.
The latest study suggests that the protective effect of the diet may kick in an even earlier stage.
The researchers found that by the time the children were six-and-a-half years old their diet appeared to have little impact on their risk of asthma and allergy.
However, their mother's diet during pregnancy appeared to be much more important.
Beneficial nutrients
Consumption of vegetables more than eight times a week, of fish more than three times a week, and of legumes more than once a week, seemed to be particularly protective.
The researchers said the Mediterranean diet tended to be well balanced and full of foods which contained beneficial vitamins and minerals.
In particular, the diet was high in antioxidants, which help to keep tissues - including those in the lungs - healthy.
Fatty acids from fish were known to help cut potentially damaging inflammation.
The Thorax study continues: "Further studies are needed to better understand the mechanisms of this protective effect and the most relevant window of exposure."
Leanne Male, assistant director of Research at the charity Asthma UK, said: "This supports our advice to pregnant mothers to eat a healthy, balanced diet.
"It is of particular significance to mothers in the UK as we have one of the highest rates of childhood asthma worldwide, with one in 10 children suffering from the condition."
