There already is a scheme for those on income support etc
Free milk, infant formula, vitamins, fruit and vegetables factsheet : Directgov - Parents
When I was pregnant mid 60s 'welfare foods' applied to all pregnant women even though working. I got milk, iron capsules and concentrated orange juice.
Since the admin of a scheme exists it would be more prudent to extend it, rather than just chuck money out - which would be subject to misuse.