- New research has shown that occasional cannabis use during pregnancy can significantly reduce a newborn’s birth weight and head circumference.
- Fetal development was impacted if cannabis exposure occurred during the first trimester, while continued use resulted in more significant changes.
- Experts say THC, the psychoactive component of cannabis, can disrupt functions that impair fetal growth.
- People are advised to quit cannabis completely before becoming pregnant.
If you’re pregnant, you likely know there are certain things you should avoid, like cigarettes, alcohol, and shellfish for example. Now, research confirms that using cannabis, even occasionally, can also have a detrimental effect on a developing fetus.
The study conducted at the Central Michigan University College of Medicine found that occasional cannabis use during pregnancy may be enough to impact fetal growth significantly.
The researchers explored how the timing of cannabis exposure during pregnancy impacts fetal development. They found that when cannabis use occurred only in the first trimester, birth weight was significantly reduced, by more than 150g on average.
What’s more, if cannabis use continued into the second trimester, the newborn’s head circumference was significantly decreased as well. The babies born after continued in-utero exposure were nearly 200g lighter, and their head circumference was nearly 1cm less than that of babies who had not been exposed.
During the study, the researchers did not have information about how much or how frequently the participants used cannabis. Therefore, the authors say more research is needed to determine whether timing or amount of use is most important when it comes to effects on newborn size.
Commenting on the research, Dr. Phoebe Dodge, the study’s first author, said, “These findings are important as newborn size is one of the strongest predictors of later child health and development.”
Based on the research, her recommendation is that people should quit cannabis completely before becoming pregnant.
The results of this study add to a growing body of research that suggests cannabinoid use during pregnancy leads to poor child outcomes.
Dr. Semiya Aziz, a UK doctor and general practitioner, isn’t surprised by these findings.
“Earlier studies have also suggested that using marijuana whilst pregnant could have a harmful impact on the fetus’ development and this research supports the notion that even the occasional use of marijuana can have a significant impact on fetal growth,” she points out.
According to Aziz, what’s most important about this research is that it reminds people of the risks.
“It’s rather worrying that some dispensaries are recommending marijuana to pregnant women to ease their symptoms of morning sickness. This definitely isn’t the first line medical treatment I would advocate as a doctor,” she says.
Why cannabis use can impact fetal development
Assessing why cannabis use during pregnancy appears to have such a significant impact on fetal development and birth weight, Aziz points to the effects of THC, the psychoactive compound found in the drug.
“THC can cross the placental barrier and reach the developing fetus,” she explains. “Therefore, it can interfere with systems which play a crucial role in regulating various physiological processes, one of which includes fetal growth.”
Aziz says disruption of any of these systems can lead to impaired nutrient and oxygen delivery to the developing fetus, potentially affecting its growth in the body.
Similarly, Abbas Kanani, a pharmacist at UK online pharmacy Chemist Click, points to one study that found cannabinoid receptors are detected very early in embryonic development.
“The endocannabinoid system appears to have important roles during the early stages associated with neuronal development and cell survival,” he explains.
“This suggests that fetal exposure to cannabis may be associated with fetal abnormalities and growth and changes in birth outcomes. This study also suggests that THC may disturb the endocrine function by altering gene transcription,” he adds.
Asked why the effects of cannabis use appear to get more severe during the later stages of pregnancy, Aziz says it has an accumulative effect.
“The accumulative effect of cannabis becomes more severe if its use continues into the later stages of pregnancy because the developing fetus undergoes rapid growth and development during these stages,” she explains.
Additional risks of cannabis use during pregnancy
Low birth weight isn’t the only risk associated with cannabis use during pregnancy.
A study published in 2020 found that cannabis use while pregnant contributed to a 2-fold higher rate of premature births before 37 weeks.
It’s also linked with an increased risk of anencephaly.
“This is one of the most severe neural tube defects,” Aziz explains. “Babies exposed to marijuana during the first month of pregnancy are at increased risk of having anencephaly.”
Meanwhile, a 2017 study suggests that marijuana use during pregnancy can affect a baby’s brain development.
“In addition, using marijuana during pregnancy could potentially mean the baby has problems after birth and could spend time in the neonatal intensive care unit (NICU),” Aziz adds.
She says problems may include withdrawal symptoms, like tremors, seizures, and vomiting within the first two weeks after birth, problems with sleep, and cognitive impairments.
However, she notes that further research is needed to explore these links.
Tips to help you quit using cannabis before pregnancy
If you’re pregnant right now or planning to be and you use cannabis, experts urge you to stop using cannabis.
Kanani says having a clear goal in mind will give you motivation and direction throughout the process.
He also says recognizing what situations, people, or emotions trigger your urge to use cannabis is an important first step. From there you’ll want to develop strategies that support you throughout your pregnancy.
“Friends, family, or support groups can offer encouragement and understanding and provide reminders and accountability,” Kanani notes. “You should surround yourself with a supportive and healthy environment during pregnancy. This includes avoiding environments where cannabis is used and minimizing exposure to second-hand smoke.”
You could also find alternative activities, like physical exercise that keep you occupied and distracted from cravings.
And if you find stopping is a bigger challenge? Consider counseling.
“Seek guidance from a medical professional who can offer direction,” Aziz advises.
Bottom line, Aziz says it’s important to consider other lifestyle factors like sleep, nutrition, mindfulness, and prenatal care so that you can prioritize not only your own health but the health of your growing baby as well.
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