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Cannabis exposure during pregnancy significantly reduces birth weight

The cultural shift towards cannabis acceptance and its increased recreational use have led to an interesting, if not concerning, trend: cannabis, or marijuana, is often suggested by dispensaries to pregnant women as a remedy for pregnancy symptoms, particularly morning sickness. 

However, the implications of this advice are yet to be fully understood, as current research presents a somewhat murky picture of marijuana’s impact on prenatal development.

In an attempt to shed light on this issue, a team of researchers embarked on a study to explore how the timing of cannabis exposure during pregnancy affects fetal development. 

According to the findings, even marijuana use restricted to the first trimester of pregnancy resulted in a noteworthy decrease in birth weight – over 150 grams on average.

Dr. Beth Bailey, professor and director of population health research at Central Michigan University and senior author of the study, commented: “We show that even when marijuana use occurred only in the first trimester of pregnancy, birth weight was significant reduced, by more than 150g on average.” 

She further revealed that if cannabis use extended into the second trimester, it resulted in a significant reduction in newborn head circumference as well.

Dr. Phoebe Dodge, the study’s lead author, emphasized the importance of these findings, stating: “These findings are important as newborn size is one of the strongest predictors of later child health and development.” 

Dr. Dodge, a recent graduate from the Central Michigan University College of Medicine and an incoming pediatric resident at University Hospitals Rainbow Babies and Children’s Hospital in Cleveland, adds her voice to a growing chorus of experts calling for more scrutiny of cannabis use during pregnancy.

The study builds upon previous research demonstrating a strong correlation between cannabis use and reduced newborn size. “Size deficits were largest among newborns exposed to marijuana throughout gestation,” said Bailey.

In this context, babies born to mothers who used cannabis throughout their pregnancy weighed nearly 200 grams less and had almost one cm smaller head circumference compared to unexposed newborns. However, this study did not identify a significant correlation between cannabis use and newborn length.

The findings, published in the journal Frontiers in Pediatrics, also provide insight into patterns of cannabis use during pregnancy. The research suggests that even occasional use – such as taking marijuana to alleviate first trimester morning sickness – could inhibit fetal growth in a manner similar to continuous use throughout pregnancy. The same holds true for individuals who unknowingly use cannabis in early pregnancy.

However, the researchers also underscored some limitations to their research. Specifically, they did not have detailed data on the frequency or volume of cannabis use among participants. Their findings relied solely on whether or not participants used marijuana at certain stages of pregnancy. 

As a result, the study could not conclusively establish whether heavy cannabis use would lead to more severe impacts on newborn growth.

The researchers stressed the need for further studies to unravel the complex relationship between the timing or amount of cannabis use and its effects on newborn size. Dr. Dodge concluded the study with a clear message: “The best recommendation is that women should be advised to quit marijuana use prior to becoming pregnant.” 

Nonetheless, quitting as soon as possible after discovering a pregnancy is a close second, potentially mitigating long-term adverse health and developmental outcomes. “There are some benefits of quitting among those who begin pregnancy using marijuana,” Dodge added.

More about the health benefits and harms of cannabis

Cannabis, often referred to as marijuana, has been used for centuries for its medicinal and recreational properties. While it can provide several health benefits, it also has potential health risks that users should be aware of.

Health Benefits of Cannabis: 

Pain Management

Cannabis contains cannabinoids, active compounds that can alleviate pain by binding to brain receptors. It’s often used to treat conditions causing chronic pain like arthritis, migraines, endometriosis, and fibromyalgia.

Mental Disorders

Medical marijuana is sometimes prescribed for mental health disorders, such as Post-Traumatic Stress Disorder (PTSD) and depression. It’s also used to manage anxiety in some patients, although the evidence on this is mixed.

Neurological and Movement Disorders

Cannabis may help treat symptoms of neurological and movement disorders, including Parkinson’s disease, epilepsy, multiple sclerosis, and Huntington’s disease. The FDA has approved Epidiolex, a CBD-based drug, for treating certain types of severe epilepsy.

Nausea and Vomiting

Cannabis, particularly the compound THC, can effectively alleviate nausea and vomiting. It’s especially useful for patients undergoing chemotherapy who don’t respond to other anti-nausea medications.

Appetite Stimulation

THC can also stimulate appetite, beneficial for individuals with conditions like HIV or cancer who struggle with weight loss or lack of appetite.

Health Risks of Cannabis: 

Mental Health Issues 

Regular or heavy use of cannabis, especially at a young age, may contribute to mental health disorders such as schizophrenia, other psychoses, and social anxiety disorders. It can also lead to an increased risk of suicidal thoughts.

Dependency and Addiction

Over time, chronic use can lead to cannabis use disorder, which is characterized by dependency and addiction. This could lead to difficulties in daily life and withdrawal symptoms during cessation.

Lung Health

Similar to tobacco smoke, cannabis smoke contains harmful chemicals that could irritate your lungs and throat and could potentially increase the risk of bronchitis, lung infections, or even lung cancer, although more research is needed on this aspect.

Cognitive Impairment

Cannabis can cause cognitive impairment affecting attention, memory, and learning, both in the short term and potentially the long term.

Cardiovascular Health

Smoking cannabis can lead to increased heart rate and blood pressure, and there is some evidence that it may increase the risk of a heart attack.

Prenatal Development Risks

As discussed in your previous question, cannabis use during pregnancy may have adverse effects on the baby’s development.

It’s important to note that while cannabis can offer health benefits, it doesn’t come without risks. If you’re considering using cannabis for medicinal purposes, consult with a healthcare provider to ensure it’s the right choice for you. They can provide you with a comprehensive understanding of how cannabis could interact with your current health situation and any other medications you’re taking.


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