Pregnant Women May Not Want to Ingest Marijuana, Study Says

Pregnant women probably want to avoid putting THC in their system for the sake of their adult children, studies are beginning to show. Research on marijuana is limited but two studies that started almost 40 years ago are suggestive that THC affects brain development in unborn children that hurts their cognitive abilities in their later years. Whether any current studies are thorough enough or accurate enough, do you think that consuming marijuana while pregnant is a good idea?

Marijuana has a healthier image than many other drugs (or, depending on who you ask, alcohol), and it can ease symptoms like nausea that tend to crop up in pregnancy. But we are accumulating evidence that marijuana is probably not a great idea to use if you’re pregnant. In particular, the THC component can affect a baby’s brain in ways that you might not notice until they are older.

If you’re looking for a simple yes/no answer on whether it’s okay to use cannabis in pregnancy, I’ll point you to this categorical no from the American Congress of Obstetricians and Gynecologists. “Although there are limitations to the data on marijuana use during pregnancy…worrisome trends do emerge,” they write. Children who were exposed to marijuana in utero are more likely to have cognitive and behavioral problems later in life. The experts I spoke with absolutely did not recommend smoking weed while you’re pregnant. If you want a yes or no, there’s your no.

But you’re probably reading this because you want to know why it’s a no, and how good the evidence is, and whether there’s any wiggle room for your situation. So here are the details.

The best known marijuana chemical is tetrahydrocannabinol (THC). It’s the main psychoactive component, the part that gets you high. THC circulates in your blood, and can cross the placenta, so the fetus is exposed to it too. THC is also fat-soluble, and can end up being incorporated into your body fat. That means that you can still have small amounts of THC circulating in your body even if you haven’t consumed any marijuana lately.

THC can also enter breast milk, and its metabolites end up in baby poop, so if you use marijuana and also breastfeed, your child is exposed to the chemical that way too.

Some of what we know about the biology of marijuana comes from studies where scientists give pure THC to animals like rats. Diana Dow-Edwards, who does animal research on how drugs affect the developing brain, says it’s well established that THC interferes with the way brain cells connect to each other. “This of course is the whole essence of the brain,” she says. “One neuron connects to the next neuron, which connects to the next.” And the more marijuana the brain is exposed to, the greater the effect on those connections.

What We Do and Don’t Know About the Safety of Marijuana in Pregnancy