A new study finds that fetal exposure to cannabinoids like CBD and THC may increase risk of obesity and high blood sugar in children.

There’s a lot we don’t know about the effects of cannabis on developing fetuses. But the percentage of pregnant women who choose to make use of cannabinoids has sky-rocketed in recent years, and there is a growing body of research dedicated to understanding the impact of cannabis use during pregnancy.

While some studies have focused on behavioral issues, the latest study out of the Colorado School of Public Health analyzes the impacts of cannabis exposure on metabolism five years after birth. The pilot study found that babies born to mothers that tested positive for cannabis were more likely to have increased fat mass and blood sugar levels by age five.

“There’s this misconception that cannabis is safe,” said study author Brianna Moore in a recent interview with CNN. “So some women may use it in pregnancy, thinking that it’s a safe alternative to other medicines, even prescribed medications.”

Her statement is backed up by a 2018 study that found cannabis dispensaries often recommend cannabis to pregnant women in their first trimester (the most vulnerable time for a developing fetus). That study, performed in Colorado, found that 70% of dispensaries gave this advice, some going so far as to state that cannabis use is safe in pregnancy, something that is far from being proven, according to Moore:

“Studies show connections between marijuana use during pregnancy and low-birth weight in babies and behavioral problems later in childhood, and there may be links to glucose and weight issues as well

Fetal Cannabis Exposure

The study led by Moore used data gleaned from the Healthy Start study, a government-funded program designed to improve health outcomes before, during, and after pregnancy across all racial, ethnic, and income differences.

Of the 103 women who were tested during pregnancy, 15% had detectable levels of various cannabinoids in their urine, including THC and CBD.

“What’s interesting, too, is that we measured this at mid-pregnancy,” Moore said. “These women very much knew they were pregnant, and they were past that first trimester where cannabis is often used for morning sickness.”

The Healthy Start data showed that, compared with babies who weren’t exposed to cannabinoids in utero, exposed children experienced a range of poorer metabolic outcomes by the age of five. These outcomes include moderately higher levels of fat, higher body mass, and higher blood sugar levels.

Interestingly, no differences were seen for fasting insulin (in the adjusted model) or for insulin resistance.

Moore explains that these findings are in line with the low birth weight that has been connected with babies exposed to cannabis in utero. “Being underweight at birth can put babies in danger of what is called postnatal catch-up growth…They’ll grow so fast they may overcompensate, which actually puts them at risk for obesity, metabolic syndrome, and Type 2 diabetes later in life.”

Fetal Cannabis Exposure 2

It’s worth noting that researching the connections between cannabis and pregnancy is complicated. For example, it’s often difficult to parse out the impacts of cannabis from the impact of smoking anything. A Vox article on the subject quotes  Marie Clare McCormick, a professor of maternal and child health at Harvard, explaining that “smoking any substance increases carbon monoxide in the blood, which reduces blood’s oxygen-carrying capacity, so not as much gets to the baby.”

Gestating a baby isn’t easy, and our understanding of how cannabis interacts with a developing fetus is limited. That being said, no cannabis dispensary should be doling out ill-advised health advice about the safety of cannabis to expectant mothers. The reality is that we don’t know all the potential long-term effects of cannabis on a child, and studies like this most recent one should give us pause.

In Moore’s words: “We would encourage women to refrain from using any cannabis while pregnant or breastfeeding to minimize adverse health effects in the offspring. More studies are needed to understand how exposure to different cannabinoids during pregnancy may impact the offspring.”