Can nicotine from tobacco get into my breastmilk?

[Note: This article is being published in draft form for use in an active research study. Its contents may be adjusted as we receive feedback from collaborating health care professionals.]

Nicotine passes into the breastmilk of individuals who use nicotine products and has a long half-life, remaining in breastmilk for upwards of 4-7 hours after use. Additionally, tobacco use during lactation can affect the nutritional content and volume of milk production. However, there are limited data evaluating the effects of nicotine use on infants during lactation and breastfeeding. Evidence is limited, but early nicotine exposure may result in impaired sleep, reduced respiratory rate, delayed neurological development, and metabolic dysfunction.

The Academy of Breastfeeding Medicine (ABM) recommend that women who use nicotine products still breastfeed with the caveat that they should be counseled to reduce or stop the use of nicotine products as much as possible while breastfeeding, especially for those who smoke or vape.¹ They assert that the benefits of breastfeeding mitigate the harms of second-hand smoke and nicotine exposure. They also consider nicotine replacement products to be compatible with breastfeeding.

Similarly, the American Academy of Pediatrics does not view maternal smoking as a contraindication to breastfeeding, although individuals should be strongly encouraged to stop smoking or to minimize infant exposure.² They consider nicotine replacement products to be compatible with breastfeeding as long as the dose is less than the number of cigarettes typically smoked. They further recommend preferential use of short-acting products such as gum or lozenges.

Nicotine in Breastmilk

A 2007 study in Stockholm, Sweden of non-smoking (n=19), smoking (n=16), and snuff using (n=2) breastfeeding mothers examined the concentration of nicotine in their infants.³ The mean nicotine concentration in the breastmilk of smoking mothers was 44 μg/L, with concentrations at 40 minutes after smoking at 51 μg/L dropping to 21 μg/L at 7 hours. The two snuff using mothers had higher levels of nicotine in their breastmilk at 89 and 99 μg/L within an hour of using dropping to 47 and 57 μg/L at 7 hours. Infants had levels of nicotine in their urine correlated to their exposure (p<0.01). Two women in the nonsmoking group had detectible levels of nicotine in their breastmilk due to their exposure to secondhand smoke from their spouse’s tobacco use (28 and 13 μg/L).

A 2018 study of breastfeeding oral moist tobacco users (n=13), smokers (n=6), and nonsmokers (n=14) measured breastmilk concentrations of nicotine.⁴ The median concentration of nicotine was higher among those using oral tobacco than smokers (38.7 μg/mL vs 24.0 μg/L). Nicotine could still be detected in 60% of oral tobacco users 11 hours after use. Nicotine was no longer detectible in the breastmilk of smokers after four hours of use.

A 2003 study of 15 breastfeeding women who were smokers introduced nicotine patches to compare nicotine concentrations when the women were smoking vs different nicotine patch dosages.⁵ Nicotine concentrations in breastmilk were not significantly different between smoking a mean of 17 cigarettes per day and the 21 mg/day patch (25.2 vs 23.0 μg/L), but concentrations decreased for the 14 mg/day and 7 mg/day patches (15.8 and 7.5 μg/L, p<0.05). Of note, all of the infants’ development was normal (assessed using the Denver Developmental Screening Test which evaluates children’s developmental progress in personal-social, fine motor-adaptive, language, and gross motor skills).

Effect on Infants

A 2007 study of 15 mother-infant pairs examined the effect of nicotine exposure on infant sleep patterns.⁶ Mothers smoked on one test day and refrained from smoking on the other, then allowing their infants to breastfeed on demand for 3.5 hours following tobacco use. The estimated dose of nicotine delivered to the infants was calculated by multiplying the volume of milk consumption by the concentration of nicotine in the breastmilk at the start of feeding sessions and taking into account the body weight of each infant. The estimated dose of nicotine delivered significantly increased from 127.1±59.8 ng/kg for the nonsmoking session to 547.9±233.0 ng/kg for the smoking session. Infants spent an average of 31.1 minutes less time sleeping when exposed to breastmilk after their mother smoked (84.6 vs 53.4 minutes). Additionally, the longest duration of sleep was an average of 23.2 minutes shorter (60.1 vs 36.9 minutes). There was a dose-dependent relationship between nicotine exposure and less time spent asleep.

A 1993 study of mother-infant pairs looked at respiratory markers in infants before and after breastfeeding from smoking (n=5) and nonsmoking mothers (n=5).⁷ Infants of smokers experienced a significant reduction in respiratory rate after feeding (mean decrease of 8.24 respirations per minute, p=0.038) while infants of nonsmokers maintained a stable respiratory rate. This change was significantly correlated with the level of nicotine in the mother’s breastmilk (p=0.004).

There are currently very few published studies examining the long-term effects of nicotine exposure on infants. There are limited data from rat models that show that early nicotine exposure may affect the endocrine system^8-10 and neurological development.^11-13

Effect on Breastmilk

Studies have examined the effect of nicotine in breastmilk and the growth of infants, but results have been mixed. However, a few studies have shown that smoking decreases the volume of milk production as well as producing less nutritional milk, although it is unclear if this is due to nicotine or other factors associated with smoking. Nutritional differences between smokers and nonsmokers include smokers having lower levels of lipids, milk fat, vitamins, and minerals while having higher levels of heavy metals.

A 1992 study compared the volume of milk production in breastfeeding mothers who smoked (n=11) and controls who didn’t smoke (n=29).¹⁴ Milk production two weeks postpartum was 406±262 mL/day in smoking mothers compared to 514±338 mL/day in nonsmoking mothers. At four weeks postpartum, nonsmokers had a mean 113±179 mL/day increase in milk production while smoking mothers experience a marginal decrease of 47±122 mL/day. Smoking status was a significant predictor of milk production when controlling for race, parity, age, weight-for-height, gestational age of infant, and frequency or duration of pumping (p=0.02).

A 2012 study comparing the composition of breastmilk found that compared to nonsmokers, those who smoked had significantly lower levels of lipids (42.45 vs 31.14 mg/mL; p=0.015) and milk protein (14.95 vs 13.10 mg/mL; p=0.048).¹⁵ Smokers also had lower levels of secreted immunoglobulin A (SIgA), although the difference was not significant (0.78 vs 1.07 mg/mL; p=0.073). A 2003 study comparing the breastmilk of smokers (n=31) to nonsmokers (n=61) over the first six months postpartum found that smokers has significantly lower levels of lipids and polyunsaturated fatty acids (total lipids 3.75 g/dL in smokers vs 4.73 in nonsmokers; p<0.05), although the calculated intake of lipids and PUFAs in infants was not significantly different.¹⁶

Studies have found that smoking individuals have higher levels of the heavy metals cadmium and lead in their breastmilk, although levels have not been found to exceed admissible dietary levels. A 2013 study (n=320) found that women who smoked or had passive exposure to cigarette smoke (n=101) had significantly more lead (1.57 vs 2.40 μg/L; p<0.05) in their breastmilk than nonsmokers, accounting for 70% of the benchmark dose limit (BMDL₀₁) for lead in infants.¹⁷ A 2004 study of 34 nonsmoking mothers, 29 mothers exposed to second-hand smoke, and 18 smokers found that cadmium levels in breastmilk among smokers and those exposed to second-hand smoke was 0.27 μg/g compared to 0.20 among nonsmokers.¹⁸

Studies have found that individuals who smoke have lower levels of vitamins and minerals in their breastmilk. A 2004 study found that compared to nonsmoking mothers (n=90), smokers (n=50) had significantly lower levels of iodine, an essential mineral for infants, both in their breastmilk (53.8 vs 26.0 mg/L; p<0.001) and in their infants’ urine (50.4 mg/L vs 33.3 mg/L; p=0.005).¹⁹ A 1998 study found that compared to nonsmokers (n=41), women who smoked (n=16) had lower levels of vitamin C (496.1 vs 241.3 μmol/L)²⁰ and vitamin E (2.30 vs 1.97 mmol/L).²¹

Nicotine Replacement Therapy

Although nicotine can be passed on to infants through breastmilk, guidelines advise that nicotine replacement therapy (NRT) is compatible with breastfeeding.^1,2 The harm reduction to both the mother and infant from smoking cessation outweighs the potential risks from NRT.

There are limited to no data evaluating the safety of pharmacotherapeutic NRT options (e.g., varenicline, buproprion) during breastfeeding. Manufacturers of varenicline advise that it may transfer into breastmilk and that breastfeeding infants should be monitored for adverse events.²² There are a handful of studies on buproprion use during lactation that have found that it does pass to infants through breastmilk, but no adverse events could be attributed to its use.²³

References

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