Marijuana Use and Breastfeeding: What You Need to Know

Marijuana Use and Breastfeeding: What We Know

A wave of marijuana legislation has rolled across the United States in recent years. As of now, 29 states and the District of Columbia have legalized medical marijuana, with eight states also permitting recreational use. Regardless of its legal status, marijuana remains the most commonly used “illicit” drug during pregnancy and lactation.

As providers, we can better support patients when we are informed about marijuana’s effects, limitations of research, and professional recommendations.

1. Cannabinoids (like THC) Pass Into Breast Milk

• THC (delta-9-tetrahydrocannabinol) is one of over 400 active chemical components in marijuana.

• Cannabinoids act on the endocannabinoid system, which influences appetite, pain, mood, and memory.

• THC is fat-soluble and enters breast milk through passive diffusion.

• THC is stored in the brain and may have both acute and cumulative neurological effects.

2. Professional Organizations Advise Against Use

Organizations including the Academy of Breastfeeding Medicine, the College of Family Physicians of Canada, and the American College of Obstetricians and Gynecologists recommend that breastfeeding women stop using marijuana.

• Screening pregnant women for substance use is standard prenatal care and may help identify those likely to continue during lactation.

• Women who report cannabis use, or test positive for THC, should be offered counseling and treatment services without punitive repercussions.

3. Research Is Limited

Research on marijuana use during breastfeeding is scarce and complicated by multiple confounding factors:

• Studies often assess non-medical-grade marijuana, which may be contaminated.

• Results usually presume the use of C. sativa, though hybrids and varying THC levels complicate findings.

• Many infants studied were exposed both in utero and during breastfeeding, making causality unclear.

• Long-term studies (beyond 1 year of age) are lacking.

4. Secondhand Exposure Is Unknown

While secondhand tobacco smoke is clearly linked to respiratory problems and SIDS, the effects of secondhand marijuana smoke on infants remain unstudied.

5. Marijuana May Reduce Milk Supply

• Prolactin is the hormone responsible for breast milk production.

• Research suggests marijuana use may inhibit prolactin, leading to reduced milk supply.

• Women with insufficient milk often supplement with formula, which reduces the benefits of exclusive breastfeeding.

6. Many Women Continue Use During Lactation

Studies show that women who use marijuana during pregnancy are likely to continue postpartum, underscoring the importance of counseling during both pregnancy and breastfeeding.

7. Counseling Is Essential

Women should be informed that:

• They should stop using marijuana while breastfeeding.

• Evidence about safety is limited and inconclusive.

• THC passes into breast milk, but its short- and long-term effects are unclear.

• Marijuana use may impair parenting ability and reduce milk supply.

• Legal repercussions (including custody issues) are possible.

• Infants should be observed for delayed motor development, lethargy, low tone, irritability, and poor sucking if exposure occurs.

• Alternatives for anxiety and depression exist that are better studied and safer during lactation.

8. Do Not Withhold Lactation Support

Breastfeeding has significant health benefits, and denying lactation support can harm both mother and baby.

• Risks may be higher for premature infants, but depriving them of human milk carries its own dangers.

• Women should be counseled but not prohibited from breastfeeding.

9. Medical Use Exists

Some women use marijuana for medical conditions such as chronic pain, cancer, PTSD, HIV/AIDS, seizure disorders, or multiple sclerosis.

• Providers should recognize that not all use is recreational.

• Women may self-medicate with non-medical-grade marijuana.

10. More Research Is Needed

Ethical limitations make studying drug use in pregnant and breastfeeding women difficult. Key questions remain:

• Does marijuana affect parenting ability?

• Does maternal marijuana use increase SIDS risk—and if so, why?

• Do different routes of marijuana use (smoking, edibles, oils) result in different levels in breast milk?

• What is the risk-benefit balance between breastfeeding with marijuana exposure versus formula feeding?

• Are there long-term developmental consequences?

Legalization may encourage more women to disclose marijuana use and enable more reliable research.

Key Takeaway

Providers should remain nonjudgmental, offer evidence-based counseling, and ensure women understand both the uncertainties and the potential risks. Supporting breastfeeding while promoting safe alternatives can help protect both maternal and infant health.

Resources

• American Academy of Pediatrics. Breastfeeding and the Use of Human Milk. 2012. Link

• Astley SJ, Little RE. Maternal Marijuana Use During Lactation and Infant Development at One Year. Neurotoxicol Teratol. 1990. PDF

• Djulus J, Moretti M, Koren G. Marijuana Use and Breastfeeding. Can Fam Physician. 2005. Article

• Metz T, Strickrath E. Marijuana Use in Pregnancy and Lactation: A Review of the Evidence. AJOG. 2015. PDF

• Murphy LL, Muñoz RM, Adrian BA, Villanúa MA. Function of Cannabinoid Receptors in Hormone Secretion. Neurobiol Dis. 1998.

• Perez-Reyes M, Wall ME. Presence of THC in Human Milk. N Engl J Med. 1982.