What actually happens if your baby drinks post-alcohol (significant amount, like hangover worthy type) breastmilk?

When a lactating woman consumes alcohol, some of that alcohol is transferred into the milk. In general, less than 2 percent of the alcohol dose consumed by the mother reaches her milk and blood. Alcohol is not stored in breast milk, however, but its level parallels that found in the maternal blood. That means that as long as the mother has substantial blood alcohol levels, the milk also will contain alcohol. Accordingly, the common practice of pumping the breasts and then discarding the milk immediately after drinking alcohol does not hasten the disappearance of alcohol from the milk as the newly produced milk still will contain alcohol as long as the mother has measurable blood alcohol levels. Peak alcohol levels both in the mother' s blood and in the milk occur approximately one-half hour to an hour after drinking and decrease thereafter, although there are considerable individual differences in the timing of peak levels and in alcohol elimination rates in both milk and blood. Therefore, lactating women should not nurse for several hours after drinking until their blood alcohol levels have declined again. The question of whether exposure to alcohol in the mother’s milk can affect an infant in the short or long term has generated much speculation in the medical community. Because alcohol is excreted only to a limited extent in breast milk, many clinicians consider occasional exposure insignificant except in rare cases of intoxication in which the mother of a breast-feeding infant drinks heavily or in which a child is inadvertently fed large amounts of alcohol in a bottle. Contrary to this perception, however, the limited research that exists to date suggests that alcohol administration through the breast milk may affect the infant in several ways, such as altering milk intake and influencing infant behavior and early development and learning.