Bakers reject suggestions bread fortified with folic acid costs more.
The Association of Bakers agreed on Tuesday to voluntarily add the vitamin to bread aimed at women.
Adding folic acid to bread is expected to help reduce the risk of babies being born with defects such as spina bifida.
The previous Labour-led Government tried to make it mandatory for folic acid to be included in bread.
Folic acid campaigner Lyall Thurston says many women cannot afford particular bread lines fortified with folic acid.
But the association says current fortified bread does not cost more.
President Laurie Powell told Morning Report that bakers are also looking at adding folic acid to budget brands of bread.