Updated June 30, 2014.

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The Infant Risk Center says that it strongly suggests that the use of marijuana in pregnancy and breastfeeding by completely avoided in all forms.

The use of marijuana (cannabis) is on the rise in the United States. Two states - Colorado and Washington - legalized cannabis by state referenda in the 2012 elections and nearly half of the remaining 50 states have laws legalizing its use in various ways.

Whether as an illegal drug of abuse or for medical purposes, more and more people are using marijuana to varying degrees. The National Institute on Drug Abuse has published research based on national surveys showing that 19% of 18-25 year olds have used marijuana in the past month, and 4.8% of those ages 26 or older have done so in the past thirty days. This, coupled with the fact that up to half of all pregnancies in North America are unplanned, has lead many pregnant and lactating women to want accurate information about whether or not marijuana has deleterious effects on a fetus or nursing baby.

THC, the active component in marijuana, readily crosses the placenta during pregnancy. When other factors (such as tobacco, alcohol, & illegal drugs as well as demographic variables) are accounted for, there is little evidence that marijuana use during pregnancy causes miscarriages, premature birth, or physical deformity, as had been postulated. Though it is recommended that all use of marijuana be avoided in pregnancy.

Research does suggest that babies born to mothers who use marijuana during pregnancy have a greater risk for negative motor, behavioral, and social development throughout childhood. There is significant evidence showing maternal use during pregnancy can affect a child's neurological development - things such as memory, verbal reasoning, visual-motor integration, problem solving skills, and more - can be impacted. Such results won't begin to be seen until age three or later. Children whose mothers used marijuana during pregnancy are more likely to display hyperactivity and impulsivity by school-age, and they are also more likely to suffer from childhood depression and anxiety. It is widely recommended that the use of marijuana during pregnancy should be avoided.

The American Academy of Pediatrics states that since marijuana can be found in breast milk and there is concern about a baby's neurobehavioral development over the long-term, marijuana should not be used during pregnancy or breastfeeding.

THC is highly lipid soluble, which means it readily passes into breast milk. The body also stores THC for weeks to months, so babies will continue to show trace amounts of the drug in their bodies for several weeks after a breastfeeding mother no longer uses it. While cannabis readily passes from breast milk to a baby's system, the amounts found in breast milk are still considered insignificant to producing psychoactive affects in a baby even with mothers who are chronic users. The effects of THC in breastfed babies have not been well studied, though the potential for high concentrations of accumulation are possible with chronic use.

A mother's breast milk supply may also be negatively impacted by marijuana use. Prolactin, a hormone that is responsible for both initiating and maintaining lactation, is reduced with marijuana use. Since prolactin is essential for milk production, a low milk supply could be yet another negative side effect. And, while using marijuana, a mother may experience hallucinations, euphoria, and then deep sleep - all of which could prevent her from taking care of her baby's needs.

Though the impact of maternal marijuana use is greater while a baby is in utero than during breastfeeding, a newborn baby's brain is rapidly growing and developing and there is a significant chance that marijuana can negatively impact this growth. not only can the THC in breast milk have a negative effect on a baby, but the environmental exposure will also impact an infant. However, in this case, breast milk will have a more ameliorating affect with its living antibodies than manufactured formula. Regardless, a mother who is breastfeeding and using marijuana should speak with her health care provider and seek appropriate counseling and help so she can continue to breastfeed her baby. Breastfeeding promotes bonding and security and its unique makeup of vitamins, minerals, and immunological properties can help a baby achieve optimum growth and development - something especially important if they have been exposed to marijuana in utero.

While individual mothers may need to discuss the risks and benefits of marijuana use during pregnancy or lactation with their health care provider, the overall message to women is that marijuana use during pregnancy and lactation should be avoided. Any woman of childbearing age should consider the potential impact of marijuana usage and either take precautions against pregnancy or discontinue its use during this time in her life. It is also important to note that in states where marijuana is illegal, child welfare services may be called in if THC is noted to be in the system of the child. This alone may be enough to warrant a mother not using marijuana during breastfeeding or pregnancy.
<sub>Sources:
Breastfeeding and the Use of Human Milk. February 27, 2012. Pediatrics.http://pediatrics.aappublications.org/content/early/2012/02/22/peds.2011-3552

Djulus, J., et al. (2005) Motherisk Update Marijuana use and breastfeeding. Canadian Family Physician, volume 51. http://www.cfp.ca/content/51/3/349.ful.pdf

Hale, T. (2012) Effects of Marijuana on the Fetus and Breastfeeding Infants. Texas Tech University Health Services Center. http://www.infantrisk.com/content/effects-marijuana-fetus-and-breastfeeding-infants.

Hale, Thomas. (2012) Medications and Mother's Milk 15^th ed. Amarillo, TX: Hale Publishing.

Learn About Marijuana: Marijuana and Reproduction/Pregnancy. Alcohol & Drug Abuse Institute, University of Washington. http://adai.uw.edu/marijuana/factsheets/reproduction.htm

National Institute on Drug Abuse, 2011 National Survey of Drug Use and Health for ages 12 and older on Marijuana/Hashish. www.drugabuse.gov/drugs-abuse/marijuana.

Porath-Waller, A.J. (2009) Clearing the Smoke on Cannabis - Maternal Cannabis Use During Pregnancy. Canadian Centre on Substance Abuse. http://www.ccsa.ca/2009%20CCSA%20Documents/ccsa0117832009_e.pdf

Walker, A. et al. (1999) Neurodevelopment and neurobehavioral sequelae of selected substances of abuse and psychiatric medications in utero. Child & Adolescent Psychiatric Clinics in North America, 8, 845-867.</sub>