Alcohol Use During Breastfeeding | Breastfeeding Medicine

Undoubtedly, everyone involved with breastfeeding has had questions from mothers about alcohol use. Alcohol is one of the most interesting chemicals with regard to breastfeeding, and a fair amount of literature exists on the topic. This column reviews available data. More complete descriptions of studies and literature references can be found in the LactMed record on alcohol.
Passage into Milk
Alcohol is an unusually small molecule compared with typical therapeutic drugs. Its molecular weight (MW) is 46 Da. Compare that to other commonly used small drug molecules such as ibuprofen (MW 206 Da) and sertraline (MW 306 Da). The fact that alcohol is a very small molecule and that it is very water soluble, means that it can pass into milk readily through a paracellular pathway with little or no restriction. Consequently, milk levels closely parallel maternal blood alcohol levels and are about 95% of the maternal blood concentration at all time points after ingestion. The 5% difference is probably a result of the fat and other nonaqueous content of milk. The peak alcohol concentration in breastmilk occurs about 1 hour after ingestion on an empty stomach, but can be delayed by an additional hour or more if the alcohol is taken with a meal. Additionally, lactation appears to affect maternal alcohol absorption. Alcohol bioavailability is about 20–25% lower in lactating women than in nonlactating women, and the peak blood alcohol level is delayed by about 20–30 minutes compared with nonlactating women. Breast pumping before alcohol ingestion also causes reduced and delayed maternal alcohol blood levels. Clinically, one study found that postpartum women, both lactating and nonlactating, felt sedated for a shorter period of time than nulliparous women after alcohol ingestion.
Unlike most drugs, the amount of alcohol eliminated per unit time is constant. Using this information, a nomogram was developed that provides an estimate of the duration of alcohol in milk.1 It shows that the time required to eliminate the alcohol from a standard drink of about 12 g of alcohol varies by maternal weight. For a 54 kg woman, 2.5 hours is required to eliminate the alcohol from her milk. For a 68 kg woman 2.25 hours is required and for an 82 kg woman, 2 hours is required. For each additional drink consumed, the same number of additional hours is required for complete elimination. A phone app called Feed Safe was developed in Australia to guide mothers on when to resume nursing after drinking.2 However, this app does not seem to be readily accessible outside of Australia.
Effects on Lactation
Acute effects
Alcohol's effect on lactation can be either direct or indirect. One direct effect is a reduction in maternal oxytocin serum levels with acute alcohol ingestion. Intravenous alcohol doses of 0.5 to 0.99 g/kg reduce oxytocin response to infant sucking by 18%; doses of 1 to 1.49 g/kg reduced the response by 62%; and doses from 1.5 to 1.99 g/kg reduced the response by 80%. For a 60 kg woman, an alcohol dose of 1 g/kg would be 60 g, equivalent to five standard drinks of 12 g, or more accurately, six drinks taken orally because of the bioavailability difference.
Studies in nursing mothers with more typical oral alcohol doses of 0.3 g/kg (about 1.5 drinks) found only a slight delay in appearance of the first drop of milk (4.4 seconds versus 2.9 seconds) using a breast pump. Once alcohol is absent from the maternal bloodstream, oxytocin response returns to normal. Alcohol's effect on oxytocin response can be overcome by giving exogenous oxytocin, indicating that alcohol affects oxytocin release rather than breast responsiveness. Naloxone can also override this effect, implying involvement of endogenous opioids.
Alcohol's effect on prolactin is more complex, with timing of prolactin measurement and genetic factors involved. Ingestion of 0.4 g/kg of alcohol increases basal serum prolactin, but has a biphasic effect after pumping. Pumping during the ascending phase of blood alcohol enhances the prolactin response, but pumping during the descending phase of blood alcohol blunts the prolactin increase. Women with a family history of alcoholism have a serum prolactin increase that is diminished in rapidity, magnitude, and duration, both with and without prior alcohol consumption. They tend to nurse their infants more frequently than mothers with no family history of alcoholism, apparently as a method of compensation.
Beer specifically has a reputation for increasing milk supply. No studies have measured prolactin or oxytocin response to beer in nursing mothers, but studies in nonpregnant, nonlactating women have been done. In one study, ingestion of 1 L of beer containing 6% alcohol increased serum prolactin by nearly 2.5-fold at 30 minutes after ingestion, but sparkling water with an equivalent amount of alcohol did not. In another study, seven women were given 800 mL of beer. Six drank beer containing 4.5% alcohol and one woman drank nonalcoholic beer. Their average peak serum prolactin increased 2.4-fold between 60 and 105 minutes after ingestion. The one woman who drank nonalcoholic beer had a comparable prolactin response. Studies in animals indicate that a polysaccharide found in barley and malt is apparently responsible for the increase in prolactin after beer ingestion. No scientific evidence exists that brewer's yeast or any vitamin in beer is responsible for increases in serum prolactin or milk production as is sometimes claimed.
Long-term effects
The effect of long-term ingestion of alcohol on the duration of breastfeeding has not been well studied. Two studies from Australia studied nursing mothers who drank alcohol. A 1-year-long survey of new mothers found that women who drank more than two standard drinks daily were twice as likely to discontinue breastfeeding by 6 months postpartum than mothers who reported use below this amount. A different prospective cohort study evaluated breastfed infants at 8 weeks and 12 months of age. Most mothers' alcohol use was considered to be moderate at 14 or fewer drinks per week. Alcohol use did not adversely affect the duration of breastfeeding.
Effects on the Infant
Acute effects
A few case reports describe adverse effects on infants who were breastfed by mothers who acutely drank large quantities of alcohol. Maternal ingestion of 750 mL of port wine in 1 day caused deep unarousable sleep, snoring, pain insensitivity, inability to suck, excessive perspiration, and a feeble pulse in an 8-day-old breastfed infant. Two other infants were reportedly breastfed by alcoholic mothers over several weeks to months. Both had excessive weight gain, attributed to pseudo-Cushing syndrome in one infant, and both had their weight normalize when taken off the mother's breast. One of the infants had been restless and sleepless for several days when he suffered from violent fits and tonic–clonic seizures that required medical treatment.
Ileus with abdominal distension was reported in three Chinese neonates whose mothers had been ingesting “chicken wine” (chicken cooked in Chinese rice wine) as a cultural custom. Two infants had measurable amounts of alcohol in their blood; the other was not assessed. The authors concluded that the ileus was caused by alcohol intoxication in the infants, although this preparation also contains numerous other ingredients.
With more typical alcohol ingestion, acute effects are more subtle. In a series of studies, investigators measured the acute effect of maternal alcohol use on their breastfed infants. Mothers drank either 0.3 g/kg of alcohol or a comparable placebo on two separate occasions. Infants who drank milk that contained alcohol consumed 20–23% less milk during the 3- or 4-hour testing session, even though the time spent at the breast and number of sucks was unchanged. Mothers could perceive no difference in milk production or nursing behavior in their infants. When infants were monitored by the mothers before and after each feeding for the following 16 hours, infants increased the number of nursings during the period of 8–12 hours after the alcohol intake such that the total amount of milk consumed during the 20-hour period did not differ between the alcohol and nonalcohol days.
In studies that measured infant sleep, infants slept more frequently and for shorter periods of time during the 3.5–4 hours after alcohol intake, whether it was after mothers drank 0.3 g/kg of alcohol before breastfeeding or infants were given their mothers' milk spiked with an amount of alcohol equivalent to that in milk at 1 hour after maternal ingestion of 0.3 g/kg of alcohol. After ingesting the alcohol-containing milk, infants were observed for 1 hour after milk ingestion. Their behavioral state changed more frequently, they slept less, cried more and startled more with the alcohol-containing milk than after consuming milk without alcohol. Mother–infant interactions were more conflictive after alcohol intake, which may partially explain increased infant arousal after maternal and infant alcohol ingestion. A study that monitored the infants during the 24-hour period after maternal alcohol ingestion revealed that the infants compensated by spending more time in rapid eye movement sleep from 3.5 to 24 hours after alcohol exposure.
Long-term effects
Long-term effects of alcohol ingestion during breastfeeding were studied in two separate populations by one group of investigators, with conflicting results. In the first study, alcohol intake of more than one drink daily during nursing decreased motor function development, but not mental development at 1 year of age. A follow-up study found no decrements in performance of 18-month-old infants who were breastfed by alcohol-consuming mothers.
A study of low socioeconomic status women in South Africa evaluated development of their children at 7 years of age. Infants were grouped by whether their mothers drank alcohol during pregnancy and breastfeeding, breastfeeding only, or who abstained during breastfeeding, according to their mothers' recall at the time of the study. Compared with the infants whose mothers reported no drinking during breastfeeding, those whose mothers reported drinking during breastfeeding had lower verbal IQ, and were lower on growth charts.
A prospective cohort study in Australia evaluated breastfed infants at 8 weeks and 12 months of age and tracked their mothers' alcohol use. Most mother's alcohol use was considered to be moderate and nursing was almost always timed to minimize the amount of alcohol in breastmilk. The infants of mothers who used alcohol postpartum had no greater risk of adverse social, mental, or motor development outcomes up to 12 months of age than the infants of mothers who were alcohol abstainers.
A subgroup analysis of a large cohort study in Norway found that the infants of mothers who drank alcohol during breastfeeding had no greater risk of asthma, allergy, or lower respiratory infections at 36 months of age than infants of mothers who did not drink.
Summary
Use of alcohol in moderate amounts, for example, one drink with a meal, is unlikely to harm a breastfed infant as long as breastfeeding or pumping does not take place too soon after alcohol intake. Waiting 2–2.5 hours per drink will minimize infant exposure. Nursing sooner than this can temporarily affect the infant's behavior. Studies on the effects of chronic moderate drinking have found conflicting results. Heavy drinking by a nursing mother can cause more serious adverse effects on the infant and interferes with letdown.