Pot & Pregnancy: What Do We Know?

Cannabis and pregnancy can be a touchy topic. It is a confluence of several deeply personal subjects: child rearing, herbal medicine, governmental authority, and moralizing around substances. Each of these on their own is a charged topic, so all wrapped up into one, emotions and personal biases can dominate the conversation instead of a rational discussion of what we actually know.

Now that the culture and social stigma is beginning to change,  honest dialogue about the potential effects of cannabis during pregnancy is only now becoming possible.

What Does Science Say?

From the limited research, we find a lot of contradictions and noncommittal conclusions. Nonetheless, let’s examine the evidence and try to separate fact from fiction.

One study of Jamaican Mothers  in the 1980s looked at the development of children from mothers who smoked cannabis or abstained. They found that differences in child development more closely correlated to environmental factors (like poverty) than cannabis.

However, a 2011 study suggested marijuana use was associated with verbal and memory deficits in young children (ages three to four) and with impulsiveness, hyperactivity, and depression as they matured.

A more recent meta-analysis (i.e. a comprehensive review of the scientific literature) from 2016 found that any adverse birth consequences like low birth-weight were more due to the use of tobacco, common among many of the cannabis-smoking mothers.

The Problem With Scientific Studies

Pregnancy is a time of rapid change and growth, and small changes in chemical balances can indeed have powerful, far-reaching effects that can influence a growing fetus the entire rest of its life.

When scientific studies examine the effects of cannabis during pregnancy on a child, they rely on self-reporting surveys from most of the study subjects. Then they look at how the birth went and how the child develops over the years. With enough data, researchers try to identify patterns or correlations.  (Of course, as the saying goes: “correlation does not (necessarily) imply causation.” So take any conclusions with a grain of salt.)

And, of course, it would be highly unethical to dose mothers with THC for the term of their pregnancy just to see what happened, so we make do with correlation-based data collection (despite its inherent limitations).

With this self-reporting, however, there is no control for the type of cannabis, whether it is CBD or THC dominant. As we now know, the biological effects of cannabis are determined by the cannabinoid profile. So if a study found that THC is harmful, it is still completely possible that CBD is beneficial.

Associated behaviors, like tobacco use, environmental toxins, exercise, the mother’s health and psychological condition, diet, and nutrition, all play acknowledged roles in the developing fetus. Teasing out which ones are responsible for what effect, however, can be challenging.

It makes for a lot of clicks to write sensationalist articles like this 2017 New York Times article: “Pregnant Women Turn to Marijuana, Perhaps Harming Infants.” Once  you dig into the article and research, there’s really no conclusive evidence.

So Should Pregnant Mothers Toke or Not?

Well, let’s start with what we do know. A developing fetus is highly sensitive to environmental factors. The growth of its brain and nervous system follows a finely balanced path based on gradients and concentrations of highly specific compounds. When we alter the composition, it almost certainly impacts development in one way or another.

When a mother smokes, the cannabinoids that enter her bloodstream most definitely pass chemicals onto the fetus and into the breastmilk. So while we may not be able to conclusively point to one particular effect (or rule others out), effects certainly occur.

From the evidence, seems unlikely that very occasional use of cannabis to treat morning sickness in the first trimester will negatively impact the development. As the brain of the fetus develops more of its endocannabinoid system later in the pregnancy, it will become more sensitive and influenced by the presence of cannabinoids, so it is perhaps best to abstain as much as possible later in the pregnancy.

Ultimately, though, the safest option to ensure proper development of the is complete abstinence from cannabis.