Ample evidence indicates that drinking alcohol during pregnancy poses a severe and avoidable risk to unborn babies. The risks of drinking alcohol while breastfeeding, however, are not well defined. Currently, some mothers are still advised by physicians, nurses, lactation consultants, family members, and friends that it is all right to drink,1 even though an acceptable level of alcohol in breast milk has never been established.

Alcohol consumed by a mother passes easily into her breast milk at concentrations similar to those found in her bloodstream. A nursing infant is actually exposed to only a fraction of the alcohol the mother ingests,2 but infants detoxify alcohol in their first weeks of life at only half the rate of adults.3

Several proven or potential adverse effects of alcohol on suckling infants have been reported, even after exposure to only moderate levels: impaired motor development,4 changes in sleep patterns,5 decrease in milk intake,6 and risk of hypoglycemia.7 In addition, drinking large amounts of alcohol could affect lactating women’s milk flow.8,9

Some report that beer aids milk production and that infants prefer alcohol-flavoured breast milk. Even though beer increases maternal milk production and alcohol enhances its flavour, evidence indicates that the presence of alcohol in breast milk has an overall effect of decreasing infant consumption by 23%.6The underlying mechanism for this reduction is unknown.

At this time, there are no known benefits of exposing nursing infants to alcohol. Although occasional drinking while nursing has not been associated with overt harm to infants, the possibility of adverse effects has not been ruled out. Occasional drinking, however, does not warrant discontinuing breastfeeding, as the benefits of breastfeeding are extensive and well recognized.10Until a safe level of alcohol in breast milk is established, no alcohol in breast milk is safest for nursing babies. It is, therefore, prudent for mothers to delay breastfeeding their babies until alcohol is completely cleared from their breast milk.

Previous guidelines for determining the time needed to eliminate alcohol from breast milk were rough estimates based on number of drinks consumed. By also taking into account mother’s weight, which affects milk-alcohol concentration, a more accurate estimate of how long a nursing mother should delay breastfeeding can be determined.