During pregnancy, many women abstain from alcohol, tobacco, and other substances because of the risks to the unborn baby. In some cases, it is necessary for physicians to make changes to a pregnant woman's prescription medications. Women who were in the midst of a struggle with addiction when they conceived may put their unborn baby at risk for birth defects and/or withdrawal. But even after giving birth, a nursing mother must be extremely careful about ingesting a number of substances, many of which can be passed on to her baby through her breast milk. Although many believe that there are numerous health benefits for both mother and baby associated with nursing, babies can even be affected by common substances like caffeine; therefore, if a prescription medicine, illegal drug, or alcohol is part of the mother's reality, it may not be in everyone's best interest.

What factors determine a drug's presence in breast milk and whether or not it is safe for the baby?

  • Type of substance (see more detailed information below).
  • Dose – higher doses are more likely to result in exposure if the mother's body is unable to metabolize the substance before it is time for a feeding.
  • Frequency of consumption/nursing – Based on a drug's half life, its peak presence in the mother's body would be the least ideal time to nurse; if a mother takes a drug frequently, the blood and milk concentration may be higher.
  • Method of administration – more or less of a substance may ultimately reach breast milk depending on how it is taken.
  • Baby's age – Premature and young babies may be at a greater risk than babies who are older, have more developed body systems, and weigh more.


Much is known about how alcohol consumption affects nursing. Although some cultures believe that drinking beer can increase milk production (some research has suggested that barley triggers the release of prolactin, a hormone associated with lactation) and catalyze a let-down (by helping the woman relax), the American Academy of Pediatrics advises that nursing mothers only consume an occasional celebratory drink. Still, many women will time their consumption of alcohol around their babies' eating schedules so that the mother's body will have metabolized the alcohol by the time the infant is ready for his or her next feeding. Others prefer to feed their babies previously expressed milk in a bottle and then "pump and dump" the milk with the alcohol in it. Another option that is becoming more popular among nursing mothers (who do not have a history of alcoholism) is purchasing a device or strips to test for alcohol content in breast milk. Whatever you decide, it is technically best to avoid passing any amount of alcohol to your baby.

Prescription Drugs

If you are taking a medication for a chronic health condition, pain after childbirth or caesarian section, or post partum depression, ask your doctor about the risk of the drug passing into your milk and harming your baby. Some drugs, like Zoloft (sertraline), pose little to no threat whereas others, such as Ativan (lorazepam) could cause sedation or other, more serious side effects in nursing infants. The Food and Drug Administration provides a more comprehensive list of prescription medicines and categorizes them according to their risk during pregnancy and when nursing.


A study from 1982 demonstrated that THC, the psychoactive substance in marijuana, is transferred to a baby through a mother's breast milk. Although the amount was only 0.8% of what the mother consumed (adjusted for weight), the level of THC in a chronic-cannabis-using mother's milk in proportion to her blood was 8 to 1. In other words, marijuana poses the greatest risk to babies of mothers who use it frequently because it can accumulate in the mother's body (fat cells) and milk and become concentrated; however, any exposure should ideally be avoided. Additional research conducted in 1990 examined babies who had been exposed to THC in this way during their first month. At the 1-year follow-up evaluation, these babies had poorer motor development than their counterparts who had not had the exposure. Some mothers report that babies who have nursed after the mother ingested marijuana seem sleepier, eat less often, and nurse for shorter periods when they do breastfeed.

Other Illegal Drugs

Cocaine is excreted in breast milk in substantial amounts; an exposed baby's symptoms may include faster heartbeat and breathing, vomiting, shaking, irritability, and dilated pupils. La Leche League advises that women who have taken cocaine interrupt nursing for at least 24 hours. A baby who has been exposed to heroin, which also is transferred through breast milk, may cause the infant to become dependent on the substance (i.e., would go through withdrawal if discontinued) and may vomit, shake, eat less, and/or be restless. Both of these drugs are contraindicated for breastfeeding mothers; keep in mind that these drugs may be contaminated with other, unknown yet potentially harmful substances.

Other Concerns

In addition to the potential problems associated with an infant ingesting milk with a substance in it, abuse of any of the substances described in this article can impair a parent's ability to care for their baby. Mothers and fathers who are drunk or high could neglect their baby (both in terms of time and finance) at best or hurt them – either intentionally or accidentally – at worst. Millions of children live in homes where the parents abuse alcohol or drugs. Some studies have shown increased rates of physical, sexual, and emotional abuse in these households. Furthermore, drugs that are smoked, like marijuana and crack, will create secondhand smoke that could also harm an infant who is exposed to the smoke. But even if a child is not directly harmed, they may be substantially affected by watching their parent lose the battle with addiction (Read The Addict Parent: What it Means for Child Development). In the long term, children of alcoholics and addicts are more likely to continue the cycle by either becoming addicted themselves or marrying someone who is.