Heavy smoking can reduce milk supply.

A study done on breastfeeding and smoking states that cigarette smoking significantly reduces breast milk production. On rare occasions cigarette smoke has caused symptoms in the breastfeeding baby such as nausea, vomiting, abdominal cramps, and diarrhea. Smoking can stop or inhibit the milk let-down reflex. Smoking has been linked to early weaning. Smoking can cause fussiness and colic. Nicotine levels in the breastfeeding mother’s blood and milk first increase and then decrease over time.

It takes is 95 minutes for half of the nicotine to be eliminated from the body, otherwise known as half-life. Breastfeeding mothers should avoid smoking just before nursing and should never smoke while feeding her baby.