Hello,  I went through your query, Yes, using progestin-only emergency contraceptive pills (like I pill or unwanted 72) once will probably not affect either the quantity or quality of the milk your breasts are producing. Although some hormones may be passed on through a mother’s breast milk, your child is not likely to experience any adverse effects from it. Better choice during breastfeeding is using condoms or copper T,  insertion, for continued protection .