It depends on all the other factors also, don't worry. If not able to breastfeed, feed the baby other healthy foods after 6 months.

Breast milk is the gold standard nutrition for babies. It has all the nutrients that are needed to provide nutrition and immunity to the baby. With advancing science, scientists have now been able to make formula feed closer to breast milk. The most complicated of nutrients in breast milk such as prebiotics, a key nutrient that helps boost infant immunity, are now available in formula feeds. There is no equvivalent to breast milk while baby's immunity is concerned, but in cases when it is insufficient or unavailable one could consider use of formula milk containing all immunonutrients such as prebiotics, DHA, ARA, nucleotides, vitamin A,C& E, beta carotene and minerals.

A formula fed baby doesn’t get the immunological support from the antibodies in breast milk. Their immunity may not be weaker than a child that’s breastfed.