Cannabis—Real Risks Identified During Pregnancy

Drugs, even those sourced directly from plants, can have side effects if misused
January 30, 2020 Updated: February 26, 2020

While the medicinal benefits of cannabis and its active ingredient tetrahydrocannabinol (THC) are often praised, we should always remember that it is a potent herbal remedy with side effects. A new study published in Scientific Reports definitively shows that regular exposure to THC during pregnancy had a negative impact on placental and fetal development.

In the past several decades, public opinion on cannabis has softened far beyond the propaganda fueled “Reefer Madness” campaigns of the 1930s. This nearly 180-degree turn in prevailing belief has coincided with varying degrees of legalization in more than half of the United States and dozens of other countries including Canada.

The medicinal value of cannabis is undeniable for a diversity of diseases ranging from chronic pain to seizures to post-traumatic stress disorder and a whole host of other disorders. It is a potent herb with medicinal qualities, and like all medicine, it possesses side effects. The fallacy of implied safety due to its natural origins is as flawed as thinking opium or hemlock use is without risk. While I certainly would not want a return to the baseless accusations and outright fabrications targeted at cannabis in the 1930s, bringing some balance back to the cannabis conversation in 2020 would be welcome.

In general, THC and cannabis have negative effects on fertility in both men and women. THC is known to affect receptors on the hypothalamus, pituitary, and internal reproductive organs—all of which are intimately involved in human reproduction.

Men who smoked cannabis at least once a week were found to have 29 percent lower sperm counts and women could have their ovulation delayed up to 3.5 days. Both factors could contribute to infertility. Based on our current knowledge about the effects of THC and cannabis, the overall effects on fertility lean more toward risk than benefit.

In the recent study, they used a rat model and human placental cells to show that a mother’s exposure to THC during pregnancy had a notable impact on both the organ development of the fetus and gene expression, which is essential to placental function. They demonstrated that regular exposure to a low-dose of THC, replicating cannabis daily use during pregnancy, led to an 8 percent reduction in birth weight and a more than 20 percent decrease in brain and liver growth.

This is the first study to provide a plausible mechanism for the direct effect of THC inhibiting placental and fetal growth while controlling for the confounding effects of low socioeconomic status. All rats were of equal social class.

The researchers characterized how THC deprives the developing fetus of oxygen and nutrients by interfering placental crossing. By studying human placental cells, the researchers found that exposure to THC caused a decrease in a glucose transporter called GLUT-1. THC prevented the placental transfer of glucose, a key nutrient, from the mother to the fetus. Reduced blood flow from mother to fetus was also suggested by noting a decrease in the number of placental blood vessels. Both of these factors were likely contributors to the growth restriction noted in the rat pups.

While the Centers for Disease Control and Prevention (CDC) clearly discourages cannabis use for pregnant women in their online guidance, many pregnant women continue to use marijuana and its THC derivatives under a misguided assumption of safety.

The CDC states that 5 percent of American women use marijuana regularly while pregnant and other studies have found that number to be as high as 22 percent in urban, poor women between 18 and 24 years old. It is not surprising that this age group had the highest usage given the nearly uninterrupted stream of positive coverage on cannabis they had been exposed to within their lifetimes.

A likely reason for the relatively high prevalence of cannabis use in pregnant women is the high incidence of nausea and vomiting during pregnancy, more commonly known as “morning sickness.” This condition is seen in up to 70 percent of pregnant women, many of whom seek treatment for the condition.

Hyperemesis gravidarum is a severe form of nausea and vomiting estimated to affect up to 3 percent of pregnant women and may require hospitalization as well as threaten the well-being of the mother and the unborn child.

The THC found in cannabis is well-known to counter the effects of nausea and vomiting, a property used by cancer patients undergoing chemotherapy for many years. In addition to this, it can also stimulate appetite to help both nauseated pregnant women and cancer patients maintain their weight throughout the course of their condition. From that perspective, it is understandable why some would choose this natural therapy as a medical treatment. Unfortunately, with the data presented in this recent study, it is not worth the risk and is contraindicated in pregnant women due to its retarding effects on placental and fetal growth.

An important distinction to make in the review of this recent study is that it didn’t address cannabidiol (CBD) usage in pregnant women. CBD is the second-most common component of the cannabis plant used by people today and has no psychoactive effects on the brain. The majority of CBD used today is derived from industrial hemp crops rather than cannabis derivatives. Industrial hemp has little to no THC content within it but is rich in CBD.

While CBD is currently presumed safe in pregnancy by many experts, the FDA urges caution. I agree with the FDA’s prudent viewpoint until more concrete medical studies have been completed to verify its safety to our unborn children.

In summary, cannabis use in pregnant women may lead to significant decreases in birth weight, and liver and brain growth in the newborn child, regardless of socioeconomic status. From a broader perspective, this is a poignant reminder that natural medicine, like all medicine, may possess a dark side with unexpected negative side effects. In this era of increasing prevalence in childhood chronic illness and developmental delay, our next generation will need all the odds stacked in their favor. All medicines, be they pharmaceutical or natural, should always be used with respect, responsibility, and a healthy caution.

Armen Nikogosian, M.D., practices functional and integrative medicine at Southwest Functional Medicine in Henderson, Nev. He is board-certified in internal medicine and a member of the Institute for Functional Medicine and the Medical Academy of Pediatric Special Needs. His practice focuses on the treatment of complex medical conditions with a special emphasis on autism spectrum disorder in children, as well as chronic gut issues and autoimmune conditions in adults.