Parenting Resources

Marijuana Use in Pregnancy

Based on data from the National Survey on Drug Use and Health, the CDC website states approximately 1 in 20 women (5%) who are pregnant in America has used marijuana during her pregnancy.  However, a study of nearly 280,000 pregnant women in Northern California, found 7% of women in 2016 tested positive for marijuana (compared with 4% in 2009).  (Young-Wolff KC, Tucker LY, et al.  Trends in Self-reported and Biochemically Tested Marijuana Use Among Pregnant Females in California from 2009-2016.  JAMA  2017; 318(24):2490 – 2491.) Pregnant adolescents are even more likely to use marijuana.

The same researchers reported this year that women who had severe morning sickness were 3.8 times more likely to use marijuana than those women who did not suffer from nausea and vomiting as the women appeared to self-medicate. (Young-Wolff KC, Sarovar V, et al.  Association of Nausea and Vomiting in Pregnancy with Prenatal Marijuana Use.  JAMA Intern Med. Published online August 20, 2018. doi:10.1001/jamainternmed.2018.358)

Unfortunately, the most active cannabinoid (THC) readily crosses the placenta, and quickly goes directly to the brain and fat cells of the unborn baby, with fetal levels of THC reaching one-tenth to one-third of maternal levels.  The endocannabinoid system of the brain that contains receptors for THC is forming as early as 5 weeks gestation – and this system plays an important role in brain development, especially the areas of the brain involved in learning, memory and emotional regulation.  There is also some evidence that unborn baby boys may be more susceptible to adverse effects of marijuana exposure.

Marijuana also directly affects the role of the placenta, making it more permeable to other toxins.  In addition, women who smoke marijuana have higher levels of carbon monoxide in their system, again directly affecting their unborn babies.

It is difficult to specifically identify medical outcomes in infants exposed only to marijuana during pregnancy, but one recent meta-analysis appeared to show that infants exposed to marijuana have a lower birth weight and an increased risk of needing admission to an intensive care unit.  Another study did not find the same results, but did find that women who smoked both marijuana and tobacco did have a high risk for premature delivery.

Given all the medical information we have on the adverse effects of marijuana on the developing adolescent brain, pregnant women are encouraged to abstain from marijuana to protect the brains of their unborn babies.  In addition, evidence is accumulating that marijuana exposure in utero has adverse effects on children later in life.  (See further information in the links below.)


A study from Colorado found that 35.8% of women who used marijuana stated they had used the drug during pregnancy and 18% had taken marijuana while breastfeeding.  Unfortunately marijuana has characteristics (protein-bound, highly lipid soluble, with low molecular weight) that allow it to easily transfer through human milk

Studies of women using marijuana while breastfeeding are limited by small numbers of patients and women’s use of other drugs (alcohol and tobacco). However, one study did show the exposed infants had lower scores in motor skills.

Hazards of Marijuana Use in...