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Evidence Review: Marijuana and Pregnancy

Can I Use Marijuana During Pregnancy?

On the surface, it seems reasonable to want to use marijuana during pregnancy- there are edible options, and it treats nausea very well. Nausea is common during pregnancy, and nausea is an indication for medical marijuana access in all relevant states. We also have some information showing that marijuana is useful for treating difficult-to-control kinds of nausea such as cancer-related nausea.

But, we also have enough data to say with considerable certainty that marijuana use during pregnancy is detrimental to baby and birth outcomes. So let us be clear from the beginning- we recommend you do not use marijuana during pregnancy. Not any kind!

Pregnancy is one of the only things that will prevent me from certifying a patient that otherwise qualifies for medical marijuana!

Summary (TL;DR)

  • Data shows that when we legalize, more women use marijuana during pregnancy.

  • Women should not use marijuana during pregnancy.

  • It doesn’t matter what kind- flower, edibles, or anything in between. It’s not just the smoking that we’re worried about — it’s the THC!

  • Women that are contemplating pregnancy or breastfeeding should not use marijuana.

  • Marijuana use is associated with numerous fetal abnormalities including preterm labor.

  • Endocannabinoid receptors are present in fetuses at 2 weeks and THC is thought to affect the infant brain.

  • Here is an easy-to-read article that neatly summarizes the research on pregnancy and marijuana use.

Many Pregnant Women Use Marijuana

You aren’t going to find any judgment here, but the fact is that many American women are choosing to use marijuana during pregnancy. I think there are probably cultural forces at play that suggest that marijuana use during pregnancy isn’t harmful. I have even seen some things on the internet that suggest edible cannabis for morning sickness.

We absolutely have enough evidence to say for sure that more American women are using marijuana during pregnancy because of legalization. It is well-validated in population-based literature conducted in the past five years (1-3). This has to do with a combination of several factors:

Why are women using marijuana during pregnancy?

  1. Increased cultural acceptance of marijuana use

  2. Widespread availability of marijuana due to legalization

  3. Lack of provider (physician) knowledge about marijuana effects in pregnancy?

What we know from our experiences with other drugs is that, in general, studies of illicit substance use underestimate their true usage in the community. So, we can almost certainly say that greater than the 6-11% of women surveyed use marijuana at some point in their pregnancy (1). This study does go on to say that 73% of women stopped using marijuana, proven by urine drug screens.

Another study examined the specific characteristics of women that utilize marijuana. It noted an 8% rate of marijuana use in the month prior to pregnancy. In the patients of this study, marital status, education level, parity, and living in a state with medical or recreational marijuana legalization or decriminalization remained independently associated with marijuana use. Those who reported marijuana use were 3-5 times more likely to also report symptoms of depression and tobacco/alcohol use before or during pregnancy than respondents who did not report marijuana use (2).

What The Research Tells Us

This may just seem like a list of characteristics, but it does have some clinical implications. If we know that patients with a history of depression have a greater risk of using marijuana when pregnant, then we should try to specifically address the issue. We also know that, in general, people with more tenuous social situations are more likely to use substances during their pregnancy, and finding a way to approach that in a non-judgmental manner will be increasingly important.

Also, as I have said many times in the past– our medical providers, as a nation, are not well-trained regarding marijuana. There is research that validates the lack of education about marijuana in medical curricula. The way we currently educate medical students and residents involves very little marijuana and there’s a big knowledge gap out there, with pseudoscience and dispensary-level advertising taking up the slack.

Just because there is a lack of awareness around a topic does not mean it should be ignored. It is important to consider all the data and make an informed decision about marijuana use during pregnancy.

Effects of Marijuana During Pregnancy

Marijuana in pregnancy does not lead to drastic clinical findings the same way that alcohol in pregnancy does. Fetal-alcohol syndrome is a well-characterized clinical entity with specific characteristics, and we know that it causes effects well into adulthood. Exposure to alcohol in utero also has dramatic effects on the pregnancy itself. Alcohol affects the risk of premature birth and placental abruption (the placenta falling off the uterus prematurely). Marijuana isn’t like that, which probably is why the stigma isn’t as bad.

However, we know that marijuana use during pregnancy is associated with poor fetal growth (4-6). A rigorous study that examined the effect of marijuana on patients in two controlled groups was published in 2020 (Bailey et al, 4). It linked maternal marijuana use in utero to worse birth outcomes of several types- low birth weight, preterm labor, and NICU admission. Of note- this was a fairly large study, performed on American children, with a control group.

“Marijuana-exposed newborns (n = 531) had significantly worse birth outcomes than controls (n = 531), weighing 218 g less, 82%, 79%, and 43% more likely to be low birth weight, preterm, or admitted to the NICU, respectively, and significantly lower Apgar scores.” -Bailey et al, 2020 (4)

Marijuana is associated with an increased chance of spontaneous preterm birth (5). This means that mothers that use marijuana can start labor before the baby is viable- at 28 weeks or less.

Another recent review and meta-analysis found that infants of women who used marijuana during pregnancy were more likely to be anemic, have lower birth weight, and require placement in neonatal intensive care than infants of mothers who did not use marijuana.

Long Term Effects on Children

We are limited with the amount of data that we have, but we do have some limited case reports that illustrate some of the theoretical changes I discussed above.

If marijuana exposure in-utero affects the baby’s brain development, then there should be some behavioral changes, right? Fetal alcohol exposure results in a classical set of physical deformities but is also well-known to cause behavioral issues as well. Poor coordination, intellectual disability, balance issues, problem-solving skills, and mood issues are felt to be associated with fetal alcohol exposure.

We know that children with in-utero marijuana exposure have different brain shapes and sizes, including thickening in the frontal cortex (5). That’s not a good thing! Studies have also shown links between prenatal marijuana exposure and impaired higher-order executive functions such as impulse control, visual memory, and attention during the school years (6).

In Summary

While more women are using marijuana during pregnancy, clinical research shows us that marijuana use, whether it be through smoking or consuming edibles, has negative impacts on fetal development. There is also some evidence linking exposure to marijuana in the womb to impaired higher-order brain functions in young children.

We love marijuana, but if you love something, you have to tell the truth about it! Do your research and remember, our doctors are here to help. If you have any questions about medical marijuana use and how to get certified in your state, make an appointment to meet with one of our certified doctors today.

~Dr. Lee


  1. Emily Lee, Ilina D. Pluym, Deanna Wong, Lorna Kwan, Vanita Varma & Rashmi Rao (2020) The impact of state legalization on rates of marijuana use in pregnancy in a universal drug screening population, The Journal of Maternal-Fetal & Neonatal Medicine, DOI: 10.1080/14767058.2020.1765157

  2. Vanessa L. Short, Dennis J. Hand, Meghan Gannon, Diane J. Abatemarco. Maternal Characteristics Associated With Preconception Marijuana Use. American Journal of Preventive Medicine. Volume 59, Issue 4. 2020. Pages 555-561

  3. Ko JY, Coy KC, Haight SC, et al. Characteristics of Marijuana Use During Pregnancy – Eight States, Pregnancy Risk Assessment Monitoring System, 2017. MMWR Morb Mortal Wkly Rep. 2020;69(32):1058-1063. Published 2020 Aug 14. doi:10.15585/mmwr.mm6932a2

  4. Bailey, B.A., Wood, D.L. & Shah, D. Impact of pregnancy marijuana use on birth outcomes: results from two matched population-based cohorts. J Perinatol 40, 1477–1482 (2020).

  5. El Marroun H, Tiemeier H, Franken IHA, et al. Prenatal cannabis and tobacco exposure in relation to brain morphology: a prospective neuroimaging study in young children. Biol Psychiatry. 2016;79 (12):971-979.

  6. Mark A. Klebanoff, Diana G. Wilkins, Sarah A. Keim. Marijuana Use during Pregnancy and Preterm Birth: A Prospective Cohort Study. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  7. Gunn JKL, Rosales CB, Center KE, et al. Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016;6(4):e009986.

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