Mandatory folate in bread has dramatically cut the rates of serious birth defects in Aboriginal children.

A Telethon Kids Institute study, published in the Australian and New Zealand Journal of Obstetrics and Gynaecology, used WA data to examine all 52,919 Aboriginal births from 1980 to 2014.

It found the prevalence of spina bifida and related anomalies had fallen by 68 per cent since mandatory fortification of all wheat flour for bread-making was introduced by the federal government in 2009.

Inadequate levels of folate are linked to devastating birth defects of the brain or spinal cord.

Lead author Professor Carol Bower said the defects usually developed in the first month of pregnancy even before many women knew they were expecting, meaning to be effective, folate intake had to be increased before pregnancy.

Folate levels are lower in Aboriginal communities, where there's less access to fresh fruit and vegetables containing the essential vitamin.