A healthy diet before pregnancy may reduce the risk of certain heart abnormalities in babies at birth, says a study.
The researchers from University of Utah quizzed around 19,000 women about the quantity and quality of their diet in the year leading up to their pregnancy.
The women were all part of the National Birth Defects Prevention Study.
Half of them had given birth to healthy babies, and half had babies with major heart abnormalities at birth between 1997 and 2009.
Previous studies suggest that multi-vitamin supplements might lower the risk while others suggest that better diet quality might make a difference to the rate of heart abnormalities at birth.
In this study, the diet quality was assessed using two validated scoring systems: the Mediterranean Diet Score, and the Diet Quality Index for Pregnancy (DQI-P).
Mothers in the top 25 percent (quartile) of diet quality had a significantly lower risk of having a baby with certain heart defects than those in the bottom 25 percent.
Better diet was associated with a 37 percent lower risk of tetralogy of Fallot and a 23 percent lower risk of atrial septal defects.
Atrial septal defects refer to holes in the wall of the septum, which divides the upper chambers (atria) of the heart.
Tetralogy of Fallot is a complex abnormality which can lead to dangerously low oxygen levels in the blood going to the rest of the body.
However, researchers said this is an observational study, so no definitive conclusions about cause and effect can be drawn, but similar associations have been found for diet before pregnancy and some other birth defects, including cleft palate and neural tube defects.
The study was published in the BMJ journal Archives of Disease in Childhood.