What Really Happens When You Use Marijuana While Pregnant

Marijuana use is becoming more prevalent across the country, and it's being used by pregnant women at a higher rate, too. But is it safe?

As of May 2021, there were 36 U.S. states that had legalized some form of marijuana use (via the National Conference of State Legislatures). The most commonly abused drug in the U.S. is marijuana, and a 2015 survey found that 22.2 million people over the age of 12 had used marijuana in the past month (via Alcohol and Drug Abuse Institute).

According to a 2017 study published in JAMA, marijuana use by pregnant women increased from 4% to 7% between 2009-2016, nearly doubling in rate and becoming the most commonly used drug during pregnancy as well. Weed products are becoming more popular during pregnancy to treat morning sickness, and many women who used weed pre-pregnancy find themselves continuing to use it after conceiving (via Vox).

What we know about marijuana use during pregnancy

According to a 2017 study conducted by the National Academies of Sciences, Engineering, and Medicine (NASEM), the active ingredient in cannabis, THC (tetrahydrocannabinol) has been proven to cross the placenta, meaning it eventually reaches the fetus. "There are many concerns about prenatal marijuana use and the potential for adverse effects on the fetus," Kelly Young-Wolff of the Kaiser Permanente Northern California Division of Research told Vox. "And although the health effects of prenatal cannabis use are complex and not well understood, no amount of cannabis has been shown to be safe during pregnancy."

According to the NASEM study, cannabis use during pregnancy can result in low birth weights. However, researchers are unclear about whether this is due to marijuana or smoking in general, as carbon monoxide increases in the blood when smoking any substance. While vaping and consuming edibles don't involve inhaling smoke, these forms still have THC, which can potentially harm a fetus (via Healthline).

What's the bottom line? The general consensus is in line with the NASEM study, which concludes that there is insufficient evidence to say whether or not prenatal cannabis use has an effect on later outcomes. However, pregnant women should take caution and consult with their healthcare providers.