New research from the University of Colorado Anschutz Medical Campus shows that pregnant women who use cannabis are more likely to have babies who weigh less.
Researchers from the Colorado School of Public Health found the prevalence of marijuana use during pregnancy in the state was 5.7 percent, about 2.7 percent in the third trimester. Prenatal cannabis use was associated with a 50 percent increased likelihood of low birth weight. That was regardless of maternal age, race/ethnicity, level of education, and tobacco use during pregnancy
“So it clearly indicates that there is something going on with some adverse effect of marijuana use during pregnancy during gestational development,” Crume said.
Their findings dovetail with other studies, but there is still a lot researchers don’t know, Crume said. However, what is known, she said, “is that cannabis use during pregnancy is associated with adverse brain development.”
The research is based on data from about 3,200 women who took 2014 and 2015 surveys that were part of the Colorado Pregnancy Risk Assessment Monitoring System.
“Other states that have legalized marijuana should be assessing prenatal exposures,” Crume said. “This is something that we need to keep an eye on as this new substance has been introduced into our population,”
Research published in late 2017 does say more soon-to-be mothers are using marijuana, perhaps to deal with things like nausea, morning sickness or anxiety. The California research found the prevalence of use in women of all ages is on the rise, especially among women younger than 24.
Dr. Larry Wolk, executive director and chief medical officer of the state health department isn’t surprised by the findings. He said it matches other research linking maternal marijuana use and low birth weight.
“The THC in marijuana likes to be absorbed by the fat cells and a baby's developing brain is the best place for that fat to deposit,” said Wolk, who’s a pediatrician. “So not only would fat be depositing in the baby's brain, but THC from marijuana would be depositing along with it.”
His best advice for pregnant moms-to-be is to avoid marijuana.
“Why take that chance? Why risk impacting or impairing your baby's development and their brain when you can just avoid it,” Wolk said.
The state’s chief medical officer noted marijuana use is much less prevalent among pregnant women compared to other substances. In 2017, Colorado found that 17 percent of pregnant women drank alcohol, and nearly seven percent smoked tobacco in the last three months of pregnancy.
One prominent marijuana industry representative declined an interview for this story, but did say pregnant women should discuss any questions they have with their doctor. He notes that packaging is required to warn of potential health risks for pregnant women. Still, he believes there may be some benefits for pregnant women in low doses.
All sides agree that much more research is needed.