(Un)safety of Marijuana in Pregnancy

Over 180 million people use cannabis for recreational or medical purposes globally, which is becoming a worsening public health issue in light of its recent legalization battles for both medicinal and recreational purposes and its ubiquitous use among adolescents and young adults, several of whom continue using it during pregnancy. Cannabis is, in fact, the most commonly illicit drug used during pregnancy with a self-reported prevalence ranging from 2% to 5% in most studies but increases to 15–28% among young, urban, socioeconomically disadvantaged women.

It is estimated that 48–60% of marijuana users continue use during pregnancy, with many women believing that it is relatively safe to use during pregnancy and less expensive than tobacco. In reality, though, we’ve been learning that cannabis in pregnancy isn’t benign and it has been reported that healthcare providers don’t routinely counsel their patients on the potential risks.

Tetrahydrocannabinol (THC), one of the psychoactive substances found in marijuana, is distributed rapidly to the brain and fat. It is known to cross the placenta, producing fetal plasma levels that were approximately 10% of maternal levels after acute exposure.

Marijuana has been associated with several adverse pregnancy outcomes, including:

•  Central Nervous System Effects: It has been shown to disrupt normal brain development and function. Animal models demonstrate that endocannabinoids play key roles in normal fetal brain development, including in neurotransmitter systems, and neuronal proliferation, migration, differentiation, and survival. Human fetuses exhibit central nervous system cannabinoid receptor type 1 as early as 14 weeks of gestation, with increasing receptor density with advancing gestational age, which suggests a role for endocannabinoids in normal human brain development;
• A Hungarian study just published this month on Biological Psychiatry points out to the correlation of prenatal marijuana exposure and the neuropsychiatric outcome in the offspring. They reviewed data from human and experimental studies to show that long-term and heavy cannabis use during pregnancy can impair brain maturation and predispose the offspring to neurodevelopmental disorders.  “Endocannabinoids regulate brain development via modulating neural proliferation, migration, and the differentiation of lineage-committed cells. In the fetal nervous system, endocannabinoid-sensing receptors and the enzymatic machinery of endocannabinoid metabolism exhibit a cellular distribution map different from that in the adult, implying distinct functions”.
•  This Dutch study emphasizes that, “Besides its well-known involvement in specific brain functions, such as control of movement, memory and emotions, the endocannabinoid system plays an important role in fundamental developmental processes such as cell proliferation, migration and differentiation. For this reason, changes in its activity during stages of high neuronal plasticity, such as the perinatal and the adolescent period, can have long-lasting neurobehavioral consequences”.
• It has repeatedly been correlated with impaired cognition and increased sensitivity to drugs of abuse; (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3988557/)
• The National Institute on Drug Abuse emphasizes that “human studies have shown that some babies born to women who used marijuana during their pregnancies respond differently to visual stimuli, tremble more, and have a high-pitched cry, which could indicate problems with neurological development. In school, children prenatally exposed to marijuana are more likely to show gaps in problem-solving skills, memory, and the ability to remain attentive. Establishing marijuana’s effects on prenatal development is important, because roughly half of U.S. pregnancies are unplanned, with the rate considerably higher for teens and young adults, so many women may use marijuana without knowing they are pregnant. Furthermore, breastfeeding mothers are cautioned that some research suggests that THC is excreted into breast milk in moderate amounts. Researchers do not yet know what this means for the baby developing brains”.
• Women who use cannabis are more likely to experience intimate partner violence; (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686908/)
• Children who were exposed to marijuana in utero had lower scores on tests of visual problem solving, visual-motor coordination, and visual analysis than children who were not exposed to marijuana in utero (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2975798/ and http://www.ncbi.nlm.nih.gov/pubmed/8727237);
• It is associated with decreased attention span and behavioral problems and is an independent predictor of marijuana use by age 14 years (http://www.ncbi.nlm.nih.gov/pubmed/16911731, http://www.ncbi.nlm.nih.gov/pubmed/10840176, http://www.ncbi.nlm.nih.gov/pubmed/1469105); and
•  Poorer reading and spelling scores and lower teacher-perceived school performance (http://www.ncbi.nlm.nih.gov/pubmed/15203174).
• At least one study showed that THC was significantly associated with stillbirth (odds ratio 2.34, 95% CI, 1.13–4.81), though this finding was somewhat confounded by the effect of cigarette smoking. It has also been shown to increase the risk of intrauterine growth restriction and low birth weight.

In light of all the evidence above, The American College of Obstetricians and Gynecologists (ACOG) issued an official recommendation in 2015 advising ob-gyns to urge their patients who are pregnant or contemplating pregnancy to discontinue marijuana use.

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Recommendations

The American College of Obstetricians and Gynecologists recommends the following:

• Before pregnancy and in early pregnancy, all women should be asked about their use of tobacco, alcohol, and other drugs, including marijuana and other medications used for nonmedical reasons.
• Women reporting marijuana use should be counseled about concerns regarding potential adverse health consequences of continued use during pregnancy.
• Women who are pregnant or contemplating pregnancy should be encouraged to discontinue marijuana use.
• Pregnant women or women contemplating pregnancy should be encouraged to discontinue use of marijuana for medicinal purposes in favor of an alternative therapy for which there are better pregnancy-specific safety data.
• There are insufficient data to evaluate the effects of marijuana use on infants during lactation and breastfeeding, and in the absence of such data, marijuana use is discouraged.

“It is important to emphasize that the purpose of screening is to allow treatment of the woman’s substance use, not to punish or prosecute her. Seeking obstetric–gynecologic care should not expose a woman to criminal or civil penalties for marijuana use, such as incarceration, involuntary commitment, loss of custody of her children, or loss of housing. Addiction is a chronic, relapsing biological and behavioral disorder with genetic components, and marijuana use is addictive in some individuals. Drug enforcement policies that deter women from seeking prenatal care are contrary to the welfare of the mother and fetus”, ACOG concludes.