Smoking cigarettes or chewing tobacco may reduce your milk production and inhibit the let-down reflex. It also may make your baby fussy or irritable. Babies who are exposed to secondhand smoke are at increased risk for many problems, including ear infections, asthma, and sudden infant death syndrome (SIDS). You should not smoke or be around those who do while you are pregnant or breast-feeding. Illegal drugs can be passed to a baby in some amount through the breast milk. Drug use can cause poor milk let-down in the mother and a lack of energy, intoxication, hyperactivity, addiction, or other health problems in the infant. Drugs can also get in the way of a mom’s ability to care for her child.