Pregnant women who smoke a joint on the daily are putting their babies at risk of being born with lower birth weights, according to new research.
A study from Queen’s University and Western University shows that rats exposed THC daily during pregnancy will give birth to offspring with lower birth weights and less developed brains and livers.
However, three weeks after birth the rat babies were fully recovered, normal and healthy, but that rapid period of recovery growth could mean trouble later on, David Natale said.
He’s an associate professor in the department of obstetricians and gynaecologists, and in the department of biomedical and molecular sciences at Queen’s University and co-author on the study, published in Scientific Reports.
When babies — rats and humans — are born small for their age it can lead to disorders later in life like type 2 diabetes and obesity, Natale told Mugglehead. The rats in the study were born at a normal time but were eight per cent smaller than rats exposed to no THC.
Daily THC exposure in the study also led to rat babies born with brains and livers 20 per cent less developed than their sober counterparts. Because both organs were similarly delayed, the disorder is known as symmetrical fetal growth restriction, which can lead to neurological deficits and things like depression and anxiety, Natale said.
To find out what these results mean for the rat’s future will require another study, as this one just focused on pregnant rats and their newborns.
What THC does to rat babies
The study’s daily dose of THC mimicked the dosage a pregnant woman might get from smoking a daily joint, which could be used to treat nausea or anxiety, co-author Daniel Hardy said. He’s an associate professor for the Schulich School of Medicine and Dentistry at Western University.
This study did not research any other cannabinoid, such as CBD, or higher doses of THC, which could closer mimic a medical cannabis patient’s dosage.
The rats were given three milligrams of THC per kilogram they weighed daily, which is a similar dose humans get from smoking cannabis, Hardy said.
The THC in the rats’ bodies restricts the amount of nutrients that pass between mom and baby, leading to underweight and underdeveloped babies, the study reads.
But after the rats are born and start feeding themselves, they put on weight and develop to a normal size within three weeks, Hardy added.
The effects of daily THC could be compared to pregnant women drinking or smoking cigarettes, Hardy noted.
“There are similarities with fetal alcohol syndrome and nicotine exposure in pregnancy,” Hardy said. “We see some similarities in terms of the effects on the brain, on the liver…. We will see if long-term these offspring develop any of the adverse neuro-behaviour effects, like FAS offspring do, and or nicotine offspring do. I think it will but we’ll have to do the long-term studies.”
Natale also compares THC exposure to FAS, but at an arms length.
The two are comparable when looking at the information women receive when they’re pregnant, he said. Because scientists haven’t discovered at what time or in what quantity drinking can cause FAS, pregnant women are told to not drink at all, he said. Using cannabis while pregnant is similar — so it’s best to avoid while pregnant, he said.
The study did not find any risk to the rat moms during their pregnancy, Natale added. That means the daily joint dosage didn’t cause miscarriages, stillbirths or premature babies.
The Internet says weed and pregnancy is fine
This study was done because not enough is known about the effects of THC on babies, Hardy said.
Similar studies have been done to explore the relationship between cannabis use and pregnancy, but those studies didn’t take into account other factors that could effect the baby’s weight, Hardy said. Factors like socioeconomic status and other drug use, like tobacco, weren’t controlled for, which made previous findings weak.
With rats you can control everything, which makes this the first study of its kind that clearly shows there are risks associated with pregnancy and cannabis use, Hardy said.
With the legalization of cannabis and the ever increasing potency of THC it’s important for people to remember science is still catching up, Natale said.
“There are lots of sites on the Internet that say, ‘Well, it’s better than other drugs for nausea or anxiety. It’s natural so therefore it’s a better approach.’ But the science isn’t there to support that,” Natale said. “What we’re worried about is because it’s legalized people will say, ‘Well, it’s legal so I can buy it so obviously it’s safe.’ And we want to get the word out — we don’t actually know that it is safe during pregnancy.”