New Study Finds Marijuana Harmful to Fetus When Taken in First Trimester of Pregnancy

A new study is revealing the significant health impact marijuana could have on a fetus in a woman’s first trimester of pregnancy.

On May 16, the College of Medicine at Central Michigan University in Mount Pleasant released findings from their study showing how marijuana use during the early stages of pregnancy could affect fetal development.

“That’s why these findings are especially important—people can often be well into the first trimester and don’t even know they are pregnant,” lead author Beth Bailey told CNN. “Our study drills down to look very specifically at a specific time point in pregnancy—the first trimester.”

“We found a significant decrease in birth weight of 154 grams. In terms of pounds, it’s about a third of a pound,” she added.

Though just slight decreases in weight, they can be early signs of health and behavioral issues as children grow and develop.

“These kids are more prone to developmental delays, higher rates of ADHD (attention deficit hyperactivity disorder), learning disabilities, and have higher rates of emotional problems,” Bailey said.

The results worsen if marijuana use is continued throughout the pregnancy. Results include decreased birth rate and reduced head circumference, which could be a sign the brain didn’t develop properly during pregnancy.

“Even when pregnant people stopped using marijuana by the third trimester, the babies were born with a smaller head circumference of about 1 centimeter (0.4 inch),” Bailey said.

“What we are telling women is that it’s not an absolute certainty that your baby’s growth will be impacted if you are using marijuana. But we do know that you are at substantially higher risk for that outcome.”

The study was conducted using medical records from 109 pregnant people who delivered at an obstetrics clinic at Central Michigan’s College of Medicine. 171 people who did not use marijuana served as the control group to compare the data.

While reducing marijuana consumption is beneficial, scientists do not have enough research to determine if the lower use of marijuana does not cause fetal harm. Bailey is advising pregnant women to avoid any form of cannabis.

“My advice to women is to avoid using marijuana at all during pregnancy and if possible stop using prior to becoming pregnant,” Bailey said.

The issue is that marijuana consumption during pregnancy is on the rise.

“With legalization there seems to be the idea that it must be safe since it’s legal, and so a lot of people continue to use during pregnancy,” Bailey said.