Women who eat healthily before and during pregnancy may cut the risk of their baby developing a heart problem, researchers believe.
The link is suggested by a study of 19,000 women in the US who were asked about their diet in the year leading up to pregnancy.
A healthy diet was one with plenty of fresh fish, fruit, nuts and vegetables.
Pregnant women and women trying to conceive are already advised to take certain supplements.
Experts recommend folic acid to reduce the risk of other birth defects like spina bifida, and vitamin D for healthy bones and teeth.
In England, the government’s Healthy Start scheme provides vouchers for pregnant women that can be used to buy milk and vegetables.
In the study, published in Archives of Diseases in Childhood Fetal & Neonatal Edition, half of the women had babies with heart problems while the other half did not.
When the researchers compared the diets of these two groups they found a healthier maternal diet was associated with a lower chance of congenital heart defects.
Pregnant women in the top 25% (quartile) of diet quality, had a lower risk of having a baby with certain heart defects – atrial septal defects and Tetralogy of Fallot – than those in the bottom 25%, even after accounting for other factors such as whether the mother took folic acid or was a smoker.
Congenital heart disease is one of the most common types of birth defect, affecting up to nine in every 1,000 babies born in the UK.
Mild defects, such as holes in the heart, often don’t need to be treated, as they may improve on their own and may not cause any further problems. But others can be more serious and some, lethal.
Victoria Taylor, senior dietitian at the British Heart Foundation, said: “This is an interesting study which highlights the importance of diet right from the start of life.
“A healthy diet before, during and after pregnancy can have benefits for both mother and child and, as seen here, the whole diet should be taken into consideration, rather than solely focusing on individual nutrients.
“Eating well isn’t a guaranteed way to avoid congenital heart defects, but this will be another factor that will motivate women planning a pregnancy to make healthy choices.”