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Counsel against marijuana use in pregnancy, breastfeeding :

August 27, 2018

Marijuana is one of the most widely used substances among pregnant women in the U.S., and pediatricians need to be able to counsel young women about its effects.

A new AAP clinical report recommends that pediatricians advise adolescents and women of childbearing age to abstain from marijuana use while pregnant or breastfeeding due to potential adverse consequences to the fetus, infant or child.

The report Marijuana Use During Pregnancy and Breastfeeding: Implications for Neonatal and Childhood Outcomes, from the Committee on Substance Use and Prevention and Section on Breastfeeding, is available at and will be published in the September issue of Pediatrics.

Growing influence

Social media tout the use of marijuana for severe nausea associated with pregnancy, and its legalization in some areas may give the false impression that it is safe.

At press time, nonmedical marijuana use was legal in nine states and the District of Columbia for adults 21 years and older. Medical marijuana was legal in 30 states and the district.

Consequently, more women are using or contemplating using marijuana while pregnant and breastfeeding. Recent data show the prevalence of “past month” marijuana use among pregnant women 18-44 years of age increased from 2.4% in 2002 to 3.9% in 2014, with 7.5% of pregnant 18- to 25-year-olds reporting use.There are no national data on use by pregnant teenagers.

Potential harms

The clinical report discusses how cannabinoids can cross the placenta and affect fetal development, as well as concerns about pregnancy outcomes and long-term consequences for the infant or child exposed to marijuana in utero. The understanding of the endocannabinoid system and its role in the development of neural circuitry early in fetal life also provides theoretical justification for the potential of marijuana substances, particularly tetrahydrocannabinol (THC), to affect neurodevelopment.

Due to ethical and legal constraints, there are no randomized trials of marijuana use during pregnancy and breastfeeding. Consequently, all data are from observational studies. The report summarizes these data, including a recent meta-analysis to determine the effect of marijuana exposure during pregnancy while controlling for tobacco use and other confounders, such as other drug use.

The authors of the meta-analysis stated that the increasing frequency of marijuana use during pregnancy may play a role in risk for adverse neonatal outcomes. They  cautioned, however, that women who use marijuana more frequently also are more likely to use higher amounts of tobacco and other drugs, which could not be accounted for completely in their review.

Two longitudinal studies have followed cohorts of infants prenatally exposed to marijuana through adolescence and early adulthood; these studies were limited in their ability to control for environmental and sociodemographic variables.

Despite the limitations, the observational studies indicate reason for concern, particularly in fetal growth, early neonatal behaviors and long-term neurodevelopmental and behavioral consequences of prenatal exposure to marijuana. Further, these studies were conducted when marijuana had a much lower potency than what is available today. Thus, the adverse consequences of prenatal exposure today may be much greater than what has been reported to date.

Impact on breastfeeding 

There are little data on the effect of marijuana use while breastfeeding.

Breastfeeding has numerous health benefits for the mother and the infant, particularly the preterm infant. Limited data show that THC does transfer into human milk, but there is no evidence for the safety or harm of marijuana use during lactation.

Additional concerns are that infants exposed through breastfeeding also may have been exposed during pregnancy and through inhalation of marijuana smoked in their presence.

Recommendations for pediatricians 

  • Inform adolescents and women of reproductive age about the lack of definitive research. Counsel about concerns regarding potential adverse effects of THC exposure, including passive smoke, on pregnant women and fetal, infant and child development. Include marijuana when discussing the need to abstain from tobacco, alcohol and other drugs during pregnancy.
  • Counsel pregnant women who are using marijuana or other cannabinoid-containing products to treat a medical condition, nausea and vomiting during pregnancy — or who are identified during screening as using marijuana — about the lack of safety data and the possible adverse effects of THC on the developing fetus.
  • Explain that even where marijuana is legal, pregnant women can be subject to child welfare investigations if they have a positive marijuana screen result.
  • Note that data are insufficient to assess the effects on infants who are exposed to maternal marijuana while breastfeeding. Inform women of the potential risk of exposure during lactation and encourage them to abstain from using any marijuana products while breastfeeding.
  • Encourage women who never have used marijuana to remain abstinent while pregnant and breastfeeding.         
  • Work with state/local health departments if legalization of marijuana has occurred or is being considered to help with constructive, nonpunitive policy and education for families.

Dr. Ryan is chair of the AAP Committee on Substance Use and Prevention (COSUP), Dr. O’Connor is a member of the AAP Section on Breastfeeding Executive Committee, and Dr. Ammerman is a former member of COSUP. They are co-authors of the clinical report.

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