Marijuana Exposure During Pregnancy Increases Risk of Low Birth Weight

Exposure to marijuana during pregnancy is associated with an increased risk of low birth weight, according to a new study of more than 9,000 pregnant individuals.

The researchers analyzed the impact of marijuana use on a combination of possible negative outcomes, including low birth weight, medically induced preterm birth, still birth and pregnancy-related high blood pressure in pregnant people. They found the risk increased by almost 30% in those who used cannabis during pregnancy. The risk grows the more marijuana a pregnant person consumes, the researchers report in JAMA.

When the researchers evaluated the outcomes individually, they found a 50% increase in the risk of low birth weight.

All of the possible negative outcomes are linked to placental function, the researchers said. Previous studies found that cannabis exposure can negatively affect the placenta, which provides nutrients and oxygen for the developing fetus.

“We found that cannabis use during pregnancy was associated with a risk of poor pregnancy outcomes,” the study’s lead author, Dr. Torri Metz of University of Utah Health, told NBC News. “And the risk increased with increasing use during pregnancy. This shows that it’s best not to use cannabis during pregnancy.”