Marijuana Use During Pregnancy And Breast Feeding


A few years ago, a researcher from a women’s health magazine asked for my views on an article they were planning to publish on marijuana and women’s health. I engaged, surmising that the editors are committed to conveying accurate information that could affect the health, employment, safety, social outcomes, and pregnancies of millions of women. I was wrong. After a lengthy phone interview and detailed written responses to questions, the article evolved into a “lost in translation” tome. Because my statements (backed by citations) were misrepresented to the extreme, I requested that my name be erased and it was. The troubling tone of the printed article suggested that women should use marijuana preemptively for good health, that marijuana enhances women’s health and that its use has few or no adverse consequences. With the obvious exception of pregnancy and lactation, marijuana’s negative effects generally are not unique to men or women. But, for women planning on becoming pregnant or are currently pregnant, it is important to be aware of the impact of marijuana on the developing fetus and child.

Marijuana and Pregnancy

Marijuana is the most commonly used illicit drug during pregnancy, with its use likely to rise as movements to “medicalize” or legalize gain traction. Approximately 3–30% of the pregnant population use marijuana, with use rates higher among young teenagers, certain demographic groups, and those with inadequate prenatal care. Among marijuana users, one study reported almost daily use by 16.2% of pregnant women, with 18.1% of pregnant women meeting criteria for a diagnosis of a cannabis use disorder. Approximately 70% of pregnant women believe there is slight or no risk of harm from using marijuana once or twice a week. Women who smoked tobacco, used alcohol and other drugs are 2 to 3 times more likely to use marijuana in the past year than nonusers.

Marijuana, Pregnancy, Teens

Pregnant teens are much more likely to have experimented with drugs and harbor alcohol, marijuana, and other illicit drug use disorders. Early adolescents (12–14 years) who are pregnant are more likely and pregnant late adolescents (ages 15–17) less likely than corresponding non-pregnant teens to be current substance users. Many pregnant teens continue to use substances, with problematic use highly prevalent among early adolescents. Yet their substance use declines dramatically as teens progress from the first to the third trimester of pregnancy.

Marijuana, Pregnancy, and the Unborn

Research suggests that the use of marijuana during pregnancy is associated with higher rates of stillbirths, preterm births, and reduced growth of the fetus. Marijuana may not only affect the course of pregnancy and growth of the fetus, but increasing evidence suggests that marijuana impacts brain development (see below). The results are not surprising, as circulating marijuana in mother’s blood crosses the placenta, enters fetal circulation, and distributes freely in the unborn. These findings in marijuana-consuming pregnant women are not uniformly observed, as negative outcomes can be confounded by other factors, including uncertain doses and frequency of use during each trimester, cigarette smoking, alcohol consumption, use of other drugs, socioeconomic status, others.

Marijuana, Pregnancy, and the Child

Because marijuana is found in breast milk, a breast-feeding mother who uses marijuana should assume that it is circulating in her newborn child. Whether exposed in utero or in breast milk, recent studies have shown that marijuana affects brain development. Once again, this is not surprising because endocannabinoids, the chemical messages produced by the brain that resemble THC (the psychoactive chemical in marijuana) are critical for brain development. Animal studies have shown that THC interferes with normal brain development, possibly by interfering with endocannabinoid-mediated guidance of brain growth. In humans, marijuana’s effects on early brain development are manifest by hyperactivity, poor cognitive function, and changes in a key signaling protein. A recent preclinical discovery (in animals) showed that offspring of parents who were exposed to THC only during adolescence, but not during mating or pregnancy, were more heroin-seeking that offspring whose parents never had THC exposure. This raises the question of whether sperm or ova of human marijuana users, even if exposed long before mating and pregnancy, will affect the behavior of their children. Other studies suggest that parental or prenatal exposure to marijuana can trigger changes with significant immunological consequences for offspring.

The Rising Tide of THC in Marijuana

Marijuana currently sold illegally, or legally in dispensaries or outlets, has much higher levels of THC than samples analyzed during the 1970s to the 1990s. Many of the studies on marijuana and pregnancy were completed during the period in which THC levels were much lower. The higher THC content of currently available marijuana (and lower content of CBD, a relatively benign non-psychoactive cannabinoid) may influence pregnancy, the developing unborn, and born child differently than marijuana distributed two to three decades ago.


Accumulating evidence suggest that marijuana use during pregnancy confers risks for the pregnancy, the unborn, and the born child. It is advisable for women not to use marijuana during pregnancy or while breast-feeding. It is also advisable to screen pregnant or pre-pregnant women comprehensively for use of marijuana and many other substances. Women of reproductive age should become familiar with the possible harms of marijuana use during pregnancy.