Fall 2020

Cannabis Use During Pregnancy

Should expectant mothers use cannabis? It’s complicated.

There’s no period in life with more rules than pregnancy. Mothers are encouraged to take extra precautions to keep themselves and their growing babies in optimal health. And while the professional guidelines for cannabis use during pregnancy are clear—don’t do it—the decision about whether to recommend or use cannabis should be carefully considered on a case-by-case basis.

There are valid reasons why pregnant women may want to continue medical cannabis use. Some have serious health issues, such as pain, seizure disorders, migraines, fibromyalgia, and irritable bowel syndrome, that they treat with cannabis. Others may use cannabis to overcome morning sickness. Still others may use cannabis, with or without prescription medications, to treat anxiety disorders that are exacerbated by pregnancy. In a study from Canada, the most common uses for cannabis during pregnancy were to treat a lack of appetite, general pain, insomnia, anxiety, depression, and fatigue.1

The research available on cannabis use during pregnancy doesn’t prove its safety. However, the research is limited and the majority of experiments have aimed at determining the harm of using cannabis during pregnancy and not to uncover any potential benefits. Thus, it’s important for cannabis practitioners to understand both the risks and benefits and to have candid conversations with patients who have been using cannabis prior to getting pregnant or who are considering using cannabis during pregnancy.

Although the Committee on Obstetric Practice recommends abstinence from cannabis during pregnancy, survey data show that use is climbing swiftly.2 Of course, there are caveats about recent reports. First, much of the data has been collected since the legalization of cannabis for medical and adult use, and it’s unlikely that women reported cannabis use to health care professionals when it was illegal (and many who use cannabis in states where it remains illegal likely still don’t report it).

Second, the stigma of discussing cannabis use with health care professionals may be waning; more women may be willing to tell their doctors, midwives, or doulas about their cannabis use. Thus, while recent numbers look significantly higher than they did in historical data, the historical data may well underrepresent the number of women who have used cannabis during pregnancy for years.

Recent data indicate that cannabis use among pregnant women more than doubled from 2002 to 2017, yet most of that use wasn’t attributed to medical recommendation. In 2017, 12% of pregnant women surveyed reported using cannabis in the past month, 3.4% of pregnant women overall reported daily or near daily use, and 5.3%, 2.5%, and 2.5% reported daily or near daily use during the first, second, and third trimesters, respectively.3

One study looked at nonmedical vs medical use of cannabis during pregnancy. Pregnant women who self-reported cannabis use before and during pregnancy were asked whether a health care professional had recommended cannabis use for a certain condition. If they answered “no,” they were classified as “nonmedical-only cannabis use.” Those answering “yes” were asked whether all cannabis use was recommended; if it was, they were classified as “medical-only cannabis use.”4

The results showed that the majority of pregnant women don’t use cannabis and those who do use it mainly for nonmedical-only purposes (4%) rather than for medical-only use (0.5%).4 This demonstrates a need for health care professionals to take more time talking to patients about cannabis use during pregnancy to ensure woman understand that there may be a medical need as well as the potential risks.

The Cons of Use During Pregnancy
Cannabis use during pregnancy has long been associated with detrimental effects on fetal growth and development. Low birthweight and length are more likely among the infants of women who use cannabis frequently, especially in the first and second trimesters. Other problems such as hypoglycemia, low Apgar scores, and, in severe cases, stillbirth, aren’t as common but have been reported.5 In one study, physicians found an increase in placental vascular resistance in both the second and third trimesters. This can disrupt the flow of oxygen rich blood through the placenta, which may be the cause of delayed growth.6

However, researchers from University of Nevada Las Vegas suggest that the adverse growth effects seen in pregnant women using cannabis may be due chemical compounds found in both tobacco and cannabis smoke. The authors concluded, “It’s likely that the exposure to the smoke, and not necessarily nicotine, which is found in tobacco, or THC, which is found in marijuana, is what leads to delayed fetal growth.”7

Although individual studies demonstrate the danger cannabis use may pose to unborn babies, the systemic review conducted by the National Academies of Sciences, Engineering, and Medicine and published in the 2017 report “The Health Effects of Cannabis and Cannabinoids” found limited evidence of statistical association between cannabis use and pregnancy and postbirth outcomes, concluding the following8:

• Limited evidence exists of a statistical association between maternal cannabis smoking and both pregnancy complications for the mother and admission of the infant to the neonatal ICU.
• There’s substantial evidence of a statistical association between maternal cannabis smoking and lower birthweight of the offspring.
• Insufficient evidence exists to support or refute a statistical association between maternal cannabis smoking and negative outcomes in the offspring (eg, sudden infant death syndrome, poor cognition/academic achievement, and later substance use).

While it’s known that THC can cross the placenta from mother to fetus, it’s unclear what kind of effect this and other cannabinoids can have on the developing human fetus. To understand the potential effects of cannabis consumption during pregnancy, other factors must be determined, such as the duration of exposure, the overall magnitude of exposure, and the extent to which the fetus and fetal brain are exposed to cannabinoids after maternal cannabis consumption.9

While the pharmacokinetics of THC and its metabolites have been studied in adult humans, little is known about maternal-fetal transfer and fetal pharmacokinetics of THC. Some researchers believe that introducing cannabinoids in utero will change the development of the baby’s endocannabinoid system by inhibiting neural development. More than one study shows that activation of CB1 receptors by THC during neuronal development influences cell proliferation, migration, and differentiation.10-12 Accordingly, THC administration to pregnant mice interfered with neuron generation, which altered the connection between the cerebral cortex and the spinal cord and produced long-lasting changes in fine motor skills of the adult offspring.11

An interesting theory about the impact of THC on brain development that hasn’t been studied in detail is whether repeated activation of cannabinoid receptors will lead to down-regulation or desensitization of the endocannabinoid system and whether this response might affect normal brain maturation and result in lifelong impairment.9

Pros of Cannabis as Medicine During Pregnancy
Even though health care professional associations are clear that they don’t support the use of cannabis during pregnancy, there’s a growing body of clinicians who know and understand that it can be used safely and effectively for certain conditions. Most advocates point to the fact that while cannabis has been associated with a negative stigma for the past few decades, before that it was used for its medical properties for hundreds, even thousands, of years. However, these proponents don’t deny the research of potentially negative outcomes. Rather, they evaluate specific situations and weigh the risks and benefits before making a recommendation.

For instance, a pregnant woman who has been managing anxiety with cannabis may want to continue to use it in order to prevent exposing her baby to high levels of stress, which could, in turn, lead to a child who is more disposed to stress and anxiety. According to the March of Dimes, stress during pregnancy can increase the chances of having a premature baby or a low-birthweight baby, both of which can lead to long-term health problems including alterations in brain development.13 Researchers from England showed decreased white matter development in the brains of babies born to mothers with high stress levels. In their conclusion, they offer an opinion that high stress isn’t diagnosed or treated as often as it should be during pregnancy and that more attention should be paid to maternal mental health in order to optimize the baby’s brain development.14

Similarly, a pregnant woman experiencing severe morning sickness may be advised to try using cannabis to control it, even if she’s never used cannabis before. In these cases, nausea and vomiting may lead to reduced nutrients getting to the baby, which may result in intrauterine growth retardation and a low birthweight.15,16 The antiemetic properties of cannabis may be a solution by which a pregnant woman can manage her food intake to better feed her baby. And for women who have been using cannabis to control otherwise untreatable conditions such as migraines, fibromyalgia, and irritable bowel syndrome, discontinuing cannabis use may put their own health at risk, thus affecting their babies’ development.

Cannabis Administration During Pregnancy
Because there are more health risks associated with smoking cannabis than with other forms of administration, most practitioners recommend that pregnant women who choose to use cannabis during pregnancy consider alternative methods of administration. Vaporization, tinctures, and edibles don’t expose mother or child to the byproducts of combustion, can deliver specific cannabinoids, and can be more easily titrated for maximum benefit with minimal exposure.

Although there’s evidence supporting both sides of the argument about cannabis use during pregnancy, it’s difficult to compare the science because it’s truly lacking on both sides. The majority of research into cannabis use during pregnancy shows that cannabis may harm both mother and fetus. In fact, the evidence linking cannabis use during pregnancy to adverse outcomes such as low birthweight and length as well as changes in neuropsychological functioning among children who were exposed to cannabis in utero continues to grow.17,18

Yet some cannabis advocates believe this is because benefits of cannabis use during pregnancy are often overlooked due to medical culture and lack of funding. Connections between conditions that are successfully treated with cannabis—such as stress and morning sickness—and risks to unborn babies’ development are getting stronger as well.

While there’s still a lot to learn, national guidelines recommend that pregnant women abstain from cannabis use before and during pregnancy.2 As cannabis use during pregnancy continues to rise, it’s critical that both the potential risks and benefits be studied rigorously in a variety of populations. Until then, cannabis practitioners and other health care professionals will have to work together to determine the best advice based on the evidence available and the situation at hand.

— Bonnie Johnson, MS, RDN, HCP, is a registered dietitian nutritionist, food industry consultant, speaker, and certified cannabis consultant. She spends much of her volunteer time educating a variety of audiences about the benefits and potential risks of using cannabis to treat chronic pain, anxiety, insomnia, and other ailments. As a consultant, she works with the food and cannabis industries to bring science-based education to health care professionals and category-changing products to market.

While there’s limited evidence about the effects of cannabis use during pregnancy, there’s even less research into the association between cannabis exposure and breast-feeding in newborns. Noted in the National Academies of Sciences, Engineering, and Medicine report, “The committee did not find a good- or fair-quality systematic review that reported on the association between cannabis exposure and breast-feeding.”1 One of the caveats to drawing any conclusions about cannabis exposure through breastmilk and how it relates to physical growth and motor or cognitive development is that newborns exposed to cannabis during lactation have probably also been exposed during pregnancy. Therefore, the effects are difficult to attribute to one exposure or the other. Nonetheless, because of the insufficient data, the American College of Obstetrics and Gynecology discourages cannabis use during breast-feeding.2

Cons of Cannabis Use During Lactation
The professional recommendation about cannabis use during pregnancy—to “encourage abstinence”—isn’t as strong as that for lactation—to “discourage use,” possibly because of the limited preclinical and clinical data regarding harmful effects. And the research that is available is somewhat contradictory. One study showed that infants exposed to cannabis via breastmilk show signs of sedation, reduced muscular tone, and poor sucking.3 On the other hand, another study found no significant differences in weaning, growth, or mental/motor development with regard to age in infants exposed to cannabis through breastmilk.4

Pharmacokinetic data show that THC is passed from the mother to the infant during breast-feeding, but the amount may be minimal.5 Moreover, in one study, none of the active form of THC was found in the urine of infants whose mothers smoked cannabis; other inactive THC metabolites were found in the feces of these infants, indicating that the THC absorbed from breastmilk may be simply metabolized and excreted in feces.

One important consideration in cannabis use during breast-feeding, especially in first-time mothers, is that cannabis smoking may reduce the hormones necessary for lactation, which may make long-term breast-feeding more difficult. Moreover, epidemiologic data show that mothers who smoke (cigarettes or cannabis) breast-feed for a shorter term than do nonsmokers.5 Also important to note is that infant exposure to secondhand smoke has its own list of harmful effects.

Pros of Cannabis Use During Lactation
Similar to their use of cannabis during pregnancy, mothers may choose to treat chronic illnesses, anxiety, and sleep disturbances with cannabis while breast-feeding. Most health care professional associations don’t support the use cannabis for any reason during breast-feeding; however, there’s too little research to determine whether it’s safe or unsafe. One thing is clear: Stress and anxiety will reduce breastmilk supply faster than will anything else in a new mother’s life. Therefore, cannabis use may be a solution for mothers concerned about breastmilk supply.

Practical Considerations
While it may seem safe to pump breastmilk and throw it away after using cannabis, THC is stored in fat cells, so it may be passed to the baby even weeks after a single use. Thus, “pumping and dumping” for a few hours or even days after using cannabis doesn’t prevent the transmission of cannabinoids to the baby. On the other hand, if stress management is the main purpose in considering the use of cannabis while breast-feeding, the anxiolytic properties of CBD may be the best choice. Recommending a THC-free, noncombustible form of CBD may be a clinically acceptable way for mothers to consume cannabinoids while breast-feeding without any known harmful effects to her newborn baby.

— BJ

1. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids. Published 2017.

2. Committee on Obstetric Practice. Committee opinion No. 722: marijuana use during pregnancy and lactation. Obstet Gynecol. 2017;130(4):e205-e209.

3. Liston J. Breastfeeding and the use of recreational drugs--alcohol, caffeine, nicotine and marijuana. Breastfeed Rev. 1998;6(2):27-30.

4. Tennes K, Avitable N, Blackard C, et al. Marijuana: prenatal and postnatal exposure in the human. NIDA Res Monogr. 1985;59:48-60.

5. Drugs and Lactation Database (LactMed) [Internet]: cannabis. PubMed website. Updated July 20, 2020.


1. Westfall RE, Janssen PA, Lucas P, Capler R. Reprint of: survey of medicinal cannabis use among childbearing women: patterns of its use in pregnancy and retroactive self-assessment of its efficacy against ‘morning sickness’. Complement Ther Clin Pract. 2009;15(4):242-246.

2. Committee on Obstetric Practice. Committee opinion No. 722: marijuana use during pregnancy and lactation. Obstet Gynecol. 2017;130(4):e205-e209.

3. Volkow ND, Han B, Compton WM, McCance-Katz EF. Self-reported medical and nonmedical cannabis use among pregnant women in the United States. JAMA. 2019;322(2):167-169.

4. Young-Wolff KC, Sarovar V, Tucker LY, et al. Self-reported daily, weekly, and monthly cannabis use among women before and during pregnancy. JAMA Netw Open. 2019;2(7):e196471.

5. The effects of marijuana on fetal development. MGH Center for Women’s Mental Health website. Published March 29, 2017. Accessed June 26, 2020.

6. El Marroun H, Tiemeier H, Steegers EAP, et al. A prospective study on intrauterine cannabis exposure and fetal blood flow. Early Hum Dev. 2010;86(4):231-236.

7. Brar BK, Patil PS, Jackson DN, Gardner MO, Alexander JM, Doyle NM. Effect of intrauterine marijuana exposure on fetal growth patterns and placental vascular resistance [published November 11, 2019]. J Matern Fetal Neonatal Med. doi: 10.1080/14767058.2019.1683541.

8. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids. Published 2017.

9. Grant KS, Petroff R, Isoherranen N, Stella N, Burbacher TM. Cannabis use during pregnancy: pharmacokinetics and effects on child development. Pharmacol Ther. 2018;182:133-151.

10. Calvigioni D, Hurd YL, Harkany T, Keimpema E. Neuronal substrates and functional consequences of prenatal cannabis exposure. Eur Child Adolesc Psychiatry. 2014;23(10):931-941.

11. de Salas-Quiroga A, Díaz-Alonso J, García-Rincón D, et al. Prenatal exposure to cannabinoids evokes long-lasting functional alterations by targeting CB1 receptors on developing cortical neurons. Proc Natl Acad Sci U S A. 2014;112(44):13693-13698.

12. Marsicano G, Goodenough S, Monory K, et al. CB1 cannabinoid receptors and on-demand defense against excitotoxicity. Science. 2003;302(5642):84-88.

13. Stress and pregnancy. March of Dimes website. Updated October 2019. Accessed June 26, 2020.

14. Lautarescu A, Pecheva D, Nosarti C, et al. Maternal prenatal stress is associated with altered uncinate fasciculus microstructure in premature neonates. Biol Psychiatry. 2020;87(6):559-569.

15. Deuchar N. Nausea and vomiting in pregnancy: a review of the problem with particular regard to psychological and social aspects. Br J Obstet Gynaecol. 1995;120(1):6-8.

16. Zhou Q, O’Brien B, Relyea J. Severity of nausea and vomiting during pregnancy: what does it predict? Birth. 1999;26(2):108-114.

17. Metz TD, Allshouse AA, Hogue CJ, et al. Maternal marijuana use, adverse pregnancy outcomes, and neonatal morbidity. Am J Obstet Gynecol. 2017;217(4):478.e1-478.e8.

18. Sharapova SR, Phillips E, Sirocco K, Kaminski JW, Leeb RT, Rolle I. Effects of prenatal marijuana exposure on neuropsychological outcomes in children aged 1-11 years: a systematic review. Paediatr Perinat Epidemiol. 2018;32(6):512-532.


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