Clinician Insight on the Use of Cannabis during Pregnancy

November 16, 2021

By Victory Rejuvenation Center

One of the frequent questions asked at the clinic is whether or not it is ok to use cannabis while pregnant. Cannabis use is rising in popularity worldwide. More people are starting to connect with the plant and use it for a wide range of conditions and situations. A large subset of people want to know if cannabis can be used safely during pregnancy, or not. As is the case with many great questions, there isn’t a firm yes or no to send people on their way with. We will highlight what is known about cannabis in pregnancy, the role of the endocannabinoid system in gestation, and considerations before thinking about using cannabis while pregnant.

Firstly and most importantly, the best things for pregnant women are healthy whole foods, clean water, and fresh air. They should limit white sugar and avoid processed foods with no nutritional value. It is advised not to ingest or smoke drugs of any kind while pregnant. This includes tobacco, alcohol, caffeine, cannabis, pharmaceuticals, opiates, and methamphetamines. That is the long and short of it. Now for specifics on the pregnancy and cannabis question.

Cannabis is the third most commonly used substance during pregnancy. [1] Pregnant women use cannabis at a higher rate during the first trimester with many reporting stopping or significantly decreasing consumption by the third trimester. [2,3] Throughout the literature, self-reported rates of cannabis use in pregnancy range from 1.2% to 27%. [2] Is this increase due to cannabis use being more in the open now? Or are more pregnant women actually using cannabis during pregnancy? The answer is probably both, with potentially more women admitting to it!

Research in pregnancy is difficult. There are ethical issues abound. There are also many confounding factors that make studying the effects of one substance incredibly challenging. Some of these considerations include the genetics and nutrition of the parents, using tobacco, alcohol, pharmaceuticals, or over-the-counter drugs, stress, religious beliefs, etc. Many of these can adversely impact pregnancy in their own right. There is also the possibility of synergistic effects when substances are used together. Ideally studies would be done on pregnant women who only use cannabis during pregnancy and no other substance. As you can imagine, that is difficult to do.

The Endocannabinoid System & Pregnancy

Cannabis has been used in obstetrics and women’s health for thousands of years. [4] The endocannabinoid system (ECS) is important for the entire nine months of pregnancy. The concern about cannabis use for unborn fetuses and newborns stems from the fact that cannabinoids cross the placenta. [5] The ECS plays an essential role for development and survival during three developmental stages of pregnancy. The first stage is throughout early gestation. Successful embryonal passage through the oviduct and implantation into the uterus requires critical enzymatic control of the endocannabinoids, specifically anandamide. Anandamide is an endocannabinoid, meaning those that are produced within the body. [6,7,8]

The second stage is during fetal life. Endocannabinoids and the CB1 receptor are important for brain development. Anandamide protects the developing brain from naturally occurring trauma-induced neuronal loss. The third stage is postnatally, where CB1 receptor activation by 2-AG (another endocannabinoid) was found to play a critical role in the initiation of milk suckling in mouse pups. This was possibly due to enabling innovation and/or activation of the tongue muscles. [6,7,8]

It is clear to see the potential for adverse fetal outcomes with prenatal cannabis exposure. There are preclinical studies that show harm, those that show no ill effects, and several that show actual benefit. There are clinical studies demonstrating potential harm and those that show no harm. [6,9,10] In general, the results are inconclusive.

Areas of Concern

The apprehension concerning cannabis use in pregnancy includes low birth weight, preterm babies, neonatal intensive care unit (NICU) admissions, neurodevelopmental outcomes, and poor school performance. There is also the consideration of predisposing children to more addiction disorders and depression, impaired executive functioning, memory and cognition, or mental illness. [11]

The only prospective clinical study that examined pure cannabis use in pregnancy was published by Dreher and colleagues in 1994. This pivotal research is highly referenced to this day. Dreher’s investigation demonstrated that cannabis-exposed babies were less irritable, more stable and socially responsive, and had better reflexes. The course of the pregnancies were similar in each group. The two groups of newborns were not significantly different according to physical examination data including birth weight and length, and gestational age. At a five year follow up, the result demonstrated that there were no significant differences in developmental testing outcomes. Dreher reported that children who were exposed to cannabis did well in preschool and had solid attendance. [12]

More recent investigation includes the NASEM report of 2017 which reviewed more than 10,000 studies done between 1999 and 2016. Researchers reported prenatal, perinatal, and neonatal findings that found:

  • There is substantial evidence of a statistical association between maternal cannabis smoking and lower birth weight of the babies. Findings for lower birth weight are consistent with the effects of non-cannabinoid substances in smoked cannabis and cigarette smoking.
  • There is limited evidence of a statistical association between maternal cannabis smoking and pregnancy complications for the mother and admission of the infant to the NICU.
  • There is insufficient evidence to support or refute a statistical association between maternal cannabis smoking and later outcomes in the offspring (e.g., sudden infant death syndrome, cognition/academic achievement, and later substance use).
  • No associations were found between in utero exposure to cannabis and: maternal diabetes, rupture of membranes, premature onset of labor, use of prenatal care, duration of labor, placental abruption, secondary arrest of labor, elevated blood pressure, hyperemesis gravidarum, maternal bleeding after 20 weeks, antepartum or postpartum hemorrhage, maternal weight gain, maternal postnatal issues, duration of maternal hospital stay or hormone concentrations. [13]

Examining the studies published since the NASEM report came out, some very compelling findings suggest caution should be used regarding cannabis use in pregnancy. This caution should be applied to any substances used during pregnancy. Better designed studies are needed. We need more cannabis-only studies. We need to examine the quantification of cannabis, including routes of administration (other than smoking), frequency, potency, dose, and timing of use. Normative findings must be compared to a true clinical assessment of the effects, especially when looking at cognitive development.

A foundational Generation R study tracked participants from fetal life to adulthood. They looked at these specific areas of research: 1) maternal health, 2) growth and physical development,  3) behavioral and cognitive development, 4) respiratory health and allergies, 5) diseases in childhood, and 6) overall health for children and their parents. The Generation R study was not just about cannabis, although they included information on cannabis use and frequency..  They investigated overall health and well-being and factors relating to the environment, genetics, epigenetics, lifestyle, nutrition, and social demographics. Numerous papers have been published from this one ongoing study. [14]

The El Marroun et al study in 2019 was one of those papers.  It looked at a subset of the Generation R study participants.  They looked at around 5,900 children from ages 7-10 years to assess the effects of cannabis exposure in utero. This information was gathered via questionnaire. Also, the mothers’ urine was tested for cannabis metabolites.[15]

The study results offered a new perspective that deserves further research. They found that maternal cannabis use is associated with childrens’ behavioral problems, but not their emotional issues.  However, according to the authors, the effects are probably not due to cannabis use. This is because both maternal and paternal cannabis use during pregnancy were found to be associated with the childrens’ behavioral problems. Since the use of cannabis by both parents led to these outcomes, researchers believed that there is a genetic component at play, rather than cannabis use.[15]

The studies on cognitive outcomes of children prenatally exposed to cannabis were reviewed by researchers Torres and Hart in 2020. They compared the scores of cannabis exposed children to the normative (the score of the general population). Children exposed to cannabis performed better on less than 1% of the normative and worse on less than 3.5% of the general population. Cognitive performance scores of cannabis-exposed groups overwhelmingly fell within the normal range. They concluded the current evidence does not suggest that prenatal cannabis exposure alone is associated with clinically significant cognitive functioning impairments. [16]

The Adverse Impact of Smoking

The NASEM report concluded there is substantial evidence of a statistical association between maternal cannabis smoking and lower birth weight of the offspring. There is also a caveat which the report clearly states. The findings for lower birth weight are consistent with the effects of non-cannabinoid substances in smoked cannabis and cigarettes. The act of smoking reduces the supply of oxygen and nutrients that pass through the placenta and leads to lower fetal birth weight. [13] 

We know that cannabis smoking has the same carcinogens and substances that cause COPD and other respiratory problems that result from smoking nicotine. The big difference is that smoking cannabis does not have the increased risk of lung cancer as nicotine does. [17,18] However, all of the other respiratory ailments that result from smoking nicotine also emerge when smoking cannabis. A study released in 2020 suggests increased risk for autism while using smoked cannabis. [19] They do not specify amount, timing, chemovar, frequency, or duration of use. That missing information is common in many studies and is important in the assessment of the impact of cannabis use during pregnancy. 

Reasons a pregnant woman may want to use cannabis

Why might some women turn to cannabis during pregnancy? Below are some of the most common reasons cannabis can be considered when other treatment options and nutritional and lifestyle considerations have been tried with no success. 

Hyperemesis gravidarum– Severe nausea and vomiting during pregnancy, called hyperemesis gravidarum, occurs in 0.3-3% of all pregnancies. It is a condition in which cannabis has clinically been shown to provide relief. Nausea, particularly the first trimester, is associated with vomiting and retching in 50% of those pregnancies. [20] Cannabis’ effect on nausea and vomiting is one of the reasons the NASEM report stated there is significant evidence. Cannabis and cannabinoids are effective for poor appetite in general. It certainly should be used to prevent hospitalization, subsequent intravenous nutrition, and all of the potential resultant complications. In this regard, cannabis use can be considered harm reduction.

Stress and anxiety– Perinatal anxiety disorder is estimated to occur between 13–21% of pregnancies, with postpartum prevalence estimated at 11–17%. [21] Maternal stress is associated with adverse outcomes. A 2020 study of 119 participants found there was a high prevalence of maternal psychological distress in healthy women. This stress can impair the brain biochemistry and brain development of the growing fetus. The researchers reported that these findings “support the need for routine mental health surveillance for all pregnant women and targeted interventions in women with elevated psychological distress.” [22] Therebefore, high stress during pregnancy needs to be treated. In addition, if SSRIs or benzodiazepines are used, there is the possibility of neonatal abstinence syndrome. Neonatal abstinence syndrome occurs in 30% of neonates exposed to SSRIs in utero. And benzodiazepines have been well known for years to cause neonatal abstinence syndrome. [23,24] However, cannabis does not cause this syndrome. Certainly in this instance cannabis can be considered harm reduction.  Therapy that evaluates the patient and provides coping mechanisms should be a part of the treatment for stress.

Depression and/or insomnia-Eighty-five percent of women experience some type of mood disturbance during the postpartum period. Lack of sleep, chronic pain, hormone imbalances, and other physical changes coupled with the sudden intense responsibility of a new life can result in significant damage to a woman’s mental health. This can make a new mother feel helpless and detached, especially when there is little in the way of support. [11,19] Cannabis is known to be a mood stabilizer and to provide relief of depression and anxiety. Cannabis utilizes not just the ECS, but serotonin receptors, adenosine receptors, and others. Specific terpenes, such as limonene, beta caryophyllene, myrcene, and linalool are also helpful for both depression and anxiety. [25]

This list is not exhaustive. A notable Canadian study in 2018 surveyed 103 women who were pregnant or had been pregnant. Over 66% of the women who report prenatal cannabis use mentioned substituting the cannabis for pharmaceuticals. They indicated that cannabis was perceived to be more acceptable than benzodiazepines to treat anxiety during pregnancy. Morning sickness was reported by 92% of the women. All reported it was at least slightly effective, while half said it was always effective. Nine women in the study experienced hyperemesis gravidarum. All of them found cannabis was effective in managing their symptoms without hospitalization. [26] 

An important point from this research is that 40% of the women surveyed indicated they did not feel comfortable discussing cannabis with their physicians. Thirty-five percent of participants reported they would not even mention it to healthcare professionals. [24] These results highlight the importance of the need for improved, non-judgmental clinician communication about cannabis use and pregnancy.

Harm Reduction

Hyperemesis gravidarum is an instance where cannabis can be used and can be considered harm reduction. Cannabis can be very helpful to avoid hospitalization or other potentially detrimental consequences. There are other instances when cannabis use in pregnancy is harm reduction, such as a patient with a seizure disorder controlling their condition with CBD. Or perhaps a patient with severe stress anxiety disorder who uses cannabis as opposed to anti-anxiety medicines or antidepressants. Or a pregnant patient with chronic pain may want to avoid opioids or other narcotics that commonly cause neonatal abstinence syndrome. [11]  

These decisions should be made by the pregnant patient and their physician. Appropriate counseling concerning using cannabis during pregnancy should be done with every woman of reproductive age who seeks medical cannabis use.

What about CBD?

Despite CBD’s accessibility, there are limited studies showing its safety during pregnancy. It is known that cannabinoids, including CBD, readily cross the placental barrier. While the use of cannabis has been well explored in terms of the effects on pregnancy and still needs much more exploration.

The use of CBD during pregnancy is far limited in the literature. A review paper published in 2020 disseminated the current understanding of CBD and its effects of pregnancy. The author elucidates the many potential benefits of CBD, including self-treatment of chronic pain, anxiety, depression, and as an antiemetic. However, there is room for concern due to the information gathered via preclinical research. One study found that CBD crossed the placenta to decrease inflammation. This showed altered protein function in the placenta upon being exposed to CBD. [27] Another cell culture study from 2013 discovered CBD might alter certain proteins’ expression in the human placenta. [28] These conclusions are speculative and not proven. Cell culture studies are done in a petri dish, meaning outside the body. Like animal studies, cell culture studies do not always translate to the human experience. Larger studies in human subjects are needed to elucidate the safety of CBD during pregnancy. 

The Importance of Nutrition

The most common reason women use cannabis in pregnancy is for nausea and vomiting. However, cannabis use doesn’t have to be the first line treatment for nausea during pregnancy. Nutrition plays a very important role in a healthy pregnancy and it is too often overlooked. Dr. Wilson-King has observed 90% of pregnant women with morning sickness see improvement just by altering their diets. 

Researchers examined data from 21 countries for the prevalence of nausea and vomiting in pregnancy. They found that countries with a high intake of sugars, sweeteners, meats, milk, eggs, stimulants such as caffeine, and processed foods had more sick pregnant women. Those with high intake of grains, beans, and lentils had less sick pregnant women. [29] Solid nutrition is the basis of a healthy pregnancy and should be examined thoroughly if a pregnant woman is experiencing nausea.

Guidelines if using cannabis during pregnancy

As mentioned earlier, the best things for pregnant women are healthy whole foods, clean water, and fresh air. It is advised not to ingest or smoke drugs of any kind while pregnant. This includes tobacco, alcohol, caffeine, cannabis, pharmaceuticals, opiates, and methamphetamines. It is advised that every pregnant woman find a knowledgeable physician to consult before using cannabis. Appropriate counseling concerning using cannabis during pregnancy should be done with every woman of reproductive age who seeks medical cannabis use.

Take Home Message

It must be understood that no woman wants to harm their child. No pregnant or breastfeeding women should be criminalized for using cannabis! There needs to be a compassionate and non-judgemental framework used by healthcare professionals to assess cannabis as a treatment option for a patient. In addition, patients who are pregnant should check in with themselves as to why they want to use cannabis and weigh the pros and cons, just as they would with any other substance.  

Preclinical research on cannabis during pregnancy is inconclusive, as are human studies. Cannabis is a medicine and should be respected as such. Sometimes that means it has to be used during pregnancy. In those instances, use it responsibly and under the direction of a physician knowledgeable in cannabis use during pregnancy.  And it may mean for others that cannabis would be better used at a later time. 

For more in depth discussion and a literature review, check out Dr. Wilson-King’s Clinical Training Module Cannabis Use in Pregnancy & Breastfeeding from the Society of Cannabis Clinicians.

© 2021 Victory Rejuvenation Center. This article cannot be reprinted without permission.


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