Answer: If a woman is suckling a child, whether she is the mother or a nurse, or suckles it free, and the quantity of her milk is small, and if fasting is harmful to her or to the child, it will not be obligatory on her to fast. And she should give one mudd of food stuffs (wheat or flour or noodles) per day to poor.
In both the cases, she will later give qadha for the fasts left out. But this rule is specifically applicable in a circumstance where this is the only way of feeding milk to the child - (as an obligatory precaution). But if there is an alternative, like, when more than one woman offer to suckle the child, then establishing this rule is a matter of Ishkal.