Health Letter, June 2015
By Sarah Sorscher, J.D., M.P.H.
One of the oldest myths about alcohol and breastfeeding is that alcohol helps with nursing by increasing milk production and allowing mothers to relax. Yet these days, many women are advised to avoid or limit alcohol consumption while nursing, and increasing numbers of nursing mothers are choosing to avoid alcohol entirely.
How much alcohol does a nursing infant actually consume when Mom drinks? Is there good evidence that consuming alcohol affects infant development? Is there a “safe” level of drinking for mom and baby? Learning the facts about alcohol and breast milk can help mothers separate myth from reality and protect their babies from potential harm.
Alcohol’s impact on milk production and consumption
Nursing mothers were once encouraged to drink alcohol, on the belief this would enhance milk production. It is easy to see how this myth might have developed: Researchers have found that infants suck more frequently in the first minute of nursing when their mothers have consumed alcohol and will drink more milk from a bottle when small amounts of alcohol are mixed in.
But these effects do not translate to higher milk consumption when breastfeeding. In fact, alcohol seems to reduce milk production, at least in the short term.
Scientists still do not fully understand the complex effects of alcohol on the hormones involved in milk production and release. Alcohol prevents the body from releasing oxytocin, the hormone that causes the muscles around the nipple to contract and eject milk, a process commonly known as “let-down.” However, alcohol also has a complicated effect on the release of prolactin, a hormone that stimulates milk production. Levels of prolactin spike if nursing occurs shortly after drinking, but subsequently dip below their normal levels if milk is expressed several hours after drinking.
The combined effect of these hormonal changes appears to be a drop in milk production, at least in the first few hours after drinking alcohol: One study showed that nursing women express nearly 10 percent less milk in the first two hours after moderate drinking (a little over one glass of wine or beer for a 150-pound woman). Several studies have shown that babies tend to get about 20 percent less breast milk if they nurse in the first four hours after the mother drinks alcohol.
The longer-term impact of alcohol on milk consumption is less clear. The few studies exploring this issue have shown that children make up for lost consumption by nursing more frequently during the period from eight to 12 hours after their mothers consumed a moderate amount of alcohol (again, a little over one drink for a 150-pound woman) and then stopped drinking. At the end of a 16-hour period following the mothers’ consumption of alcohol, the infants’ average overall consumption of milk was not significantly different compared with a similar period when their mothers did not drink.
Alcohol exposure for the nursing infant
Several factors influence the infant’s exposure to alcohol: the concentration of alcohol in the mother’s breast milk, the infant’s weight and the baby’s ability to remove alcohol from his or her own blood.
The alcohol concentration in milk is almost exactly the same as the concentration in the mother’s blood, which is many times lower than the concentration of alcohol in an alcoholic beverage. This means that if a woman’s blood alcohol level is 0.08 percent, the typical legal limit for driving, her milk will also contain 0.08 percent alcohol. If this milk were to be bottled and sold as a beverage in stores, it would be considered “non-alcoholic:” the typical standard for a “non-alcoholic” or low-alcohol beer is 0.5 percent or lower.
Because nursing infants are much smaller than adults, they will have significantly higher blood alcohol levels per dose of alcohol consumed. But even taking into account the baby’s very small weight, overall blood alcohol levels generally will still be very low in infants who nurse soon after their mothers consume alcohol. For example, even if a nursing mother weighing about 155 pounds were to gulp down four glasses of wine and her 13-pound baby were to nurse shortly afterward, the baby’s blood would typically reach a blood alcohol level of less than 0.005 percent, which is still incredibly low. (This point can be confusing: While the alcohol levels in breast milk are the same as the levels of alcohol in the mother’s blood, the infant’s blood levels are much lower than the level of alcohol in the breast milk he or she consumes).
The last factor to consider is the baby’s ability to process alcohol out of the blood. Newborn infants have greater difficulty eliminating alcohol from their bodies than do healthy adults. One study of newborns found that these infants were able to eliminate alcohol at about half the speed as their mothers. However, infants’ ability to process alcohol appears to improve dramatically with age: Reports from several cases in which infants accidentally swallowed large amounts of alcohol provide evidence that 2-month-old babies are able to process alcohol at the same rate as adults, and some older babies (from about 6 months onward) and toddlers appear to eliminate alcohol at a faster rate than adults., 
Health impact on infants
Data assessing the safety of alcohol exposure for nursing infants are limited, particularly regarding long-term impacts.
Alcohol consumption does appear to have some short-term effects on infant behavior. In addition to affecting consumption of milk, alcohol also alters infants’ sleep patterns by changing their levels of brain activity during sleep and making sleep-wake cycles shorter and more frequent. However, it is not clear whether alcohol actually affects the overall amount of time infants spend sleeping. One small study indicated that infants sleep about 25 percent less in the first 3.5 hours after ingesting alcohol, but other small studies have not detected an impact on the amount of time spent sleeping., 
Long-term effects are less clear. One often-cited study provided evidence that the 1-year-old infants of mothers who drink more heavily score lower in terms of motor skill development, but not mental development. However, for children whose mothers drank less than one alcoholic drink per day, the average drop in motor development scores represented 2 points or less on a scale that exceeded 120, a difference that is unlikely to be clinically meaningful. A more recent study attempting to measure these effects among 18-month old toddlers showed no relationship between alcohol consumption and motor skill development, and certain other types of development scores (hearing and speech, social/personal, and performance) were actually slightly higher in infants whose mothers drank alcohol.
Another study that is sometimes used as evidence of alcohol’s long-term impact on child development showed that when women in rural Mexico drank large amounts of “pulque,” a beverage with low alcohol content, their children had slower gains in weight and height. The authors of the study thought this effect might have been due to alcohol’s effects on milk production and consumption.
All of the studies exploring the long-term effects of alcohol on infant development suffer from a similar flaw: They are all observational, meaning the researchers documented women’s existing practices without asking them to change their alcohol-drinking behavior (mostly because it would be unethical and impractical to do so). This makes it impossible to say for certain whether higher alcohol consumption actually caused any of the negative effects observed. It could have been mere chance that women who drank more in these studies also tended to have other traits that could influence health outcomes, such as older age, smoking, consumption of other drugs or some other unmeasured factor.
One thing is relatively clear: Regular, extreme heavy drinking can lead to negative health effects on a nursing infant. There has been at least one report of a breastfeeding infant who displayed the signs and symptoms of a condition associated with increased cortisone levels in the body related to alcoholism, but whose symptoms vanished after the mother reduced her alcohol consumption. That child’s mother regularly drank extreme amounts of alcohol, averaging more than seven cans of beer per day.
Advice for nursing mothers
There is little published evidence that consuming alcohol in moderation while breastfeeding is harmful to infant health. Nevertheless, alcohol does have a noticeable impact on short-term behavior for infants, and extreme, heavy drinking has been linked to harm. Because there have been so few high-quality studies assessing the impact of alcohol consumption on infant health, the safest approach for nursing mothers is to abstain from drinking alcohol, or drink only occasionally and in moderation.
The American Academy of Pediatrics recommends minimizing alcohol consumption and drinking only occasionally, with a maximum consumption of two beers or less for a mother who weighs about 130 pounds. The group also recommends that mothers refrain from nursing for two hours after drinking alcohol, to minimize the amount of alcohol ingested in milk.
In addition, Health Letter strongly recommends that nursing mothers avoid drinking alcohol from birth until the infant is two months of age, as newborns have an impaired ability to process alcohol. Women are already strongly advised not to drink alcohol during pregnancy because of known negative health impacts on the developing fetus. Extending this restriction for an additional two months should not be overly burdensome for most women.
Because alcohol will eventually clear from the milk over time, it is generally not necessary to “pump and dump,” a practice used by some mothers to express and then dispose of breast milk thought to contain alcohol. The only time this practice might be useful is if a mother needs to pump in order to maintain milk supply or avoid discomfort. Mothers who are concerned about delaying nursing following alcohol consumption can also express milk in advance and then bottle-feed during the period when levels of alcohol in the milk remain high.
 American Academy of Pediatrics. Policy Statement: Breastfeeding and the Use of Human Milk. http://pediatrics.aappublications.org/content/129/3/e827.full. Accessed May 21, 2015.