"Our study supports these guidelines, as we found no increased risk of asthma if folic acid supplements were taken in pre or early pregnancy," Associate Professor Davies says. However, these guidelines may need to be expanded to include recommendations about avoiding use of high dose supplemental folic acid in late pregnancy."

He says their study found no evidence to link asthma with dietary folate, which is found in green, leafy vegetables, certain fruits and nuts.

Nearly half of all mothers in the study took a folic acid supplement pre-pregnancy and 56% met the required daily dosage of 400 micrograms in early pregnancy.

"These findings show there is a potentially important critical period during which folic acid supplement dosages may be manipulated to optimise their neuro-protective effects while not increasing the risk of asthma," Associate Professor Davies says.

Source: University of Adelaide