What happens if the mother does not eat anything containing dha than there is none for the breast milk right?

Correct: This is correct. DHA in the breast milk comes from DHA in the diet. There are studies globally which evaluate the level of DHA in mother's milk. It is interesting to see the variation. Coastal area locations of note yield mothers DHA in milk to be at high levels. Sub saharan land locked African countries of note yield mothers milk DHA to be at low levels.