What We Know About Smoking Weed While Pregnant [2024 Update]

weed and pregnancy
By Rebecca Olmos Updated March 8th

Medically reviewed by Dr. Brian Kessler, MD

Consuming cannabis can be an extremely personal decision. This is particularly true if you need to consider certain aspects of your health and well-being. The decision on whether or not to smoke weed can be made even more personal if there is a pregnancy to consider. To compound this issue, there are many myths and questions regarding smoking marijuana while pregnant.

It is commonly understood that smoking any substance while pregnant can be harmful. But with cannabis research hampered by the drug's federal Schedule I status, many peer-reviewed studies on smoking while pregnant focused on the use of tobacco and other narcotics. Meanwhile, studies looking specifically at the effects of smoking cannabis while pregnant remain in the early stages. 

In this article, we aim to provide information about the possible health impacts of cannabis use while pregnant. This is not a substitution for professional medical advice. 

What Science Says About Marijuana and Pregnancy

Pregnancy is a sensitive time during human development for both the mother and child. Studies have shown that cannabis can affect a range of biological factors that may play a role in fetal development. 

There is also the question of whether or not smoking cannabis can affect things like breastfeeding and birth control, as well as how it differs from smoking cigarettes. 

Can Smoking Weed Affect Fetal Development?

Smoking Weed While Pregnant

Fetal development refers to the stages of growth that happen to the fetus from fertilization to the end of pregnancy. The development is divided into three stages: germinal, embryonic, and fetal. 

The endocannabinoid system – the system responsible for how the body processes cannabinoids like THC and CBD – was discovered in humans in 1988 and is widely recognized as a receptor system and regulator of homeostasis in the human body. However, it isn’t well known when humans grow this system in the developmental process. And that raises questions about how cannabinoids in the mother’s blood might affect fetal development.¹

In 2003, researchers used autoradiography to study the development of CB1 receptor expression in different areas of the developing human brain. They found a significant amount of cannabinoid receptors at 19 weeks gestation, which suggests the endocannabinoid system's role in fetal development.

Another study looked at fetal human brains and found low appearances of cannabinoid receptors as early as 14 weeks gestation. They concluded that these results might explain the “mild and selective nature of postnatal neurobehavioral deficits observed in infants exposed to cannabinoids in utero.”²

Studies have also suggested that exposure to cannabis in utero may be linked to problems later in development, like visual problem-solving and behavioral issues.³ A study on 13 to 16-year-olds that had prenatal exposure to marijuana displayed issues with attention span.⁴ A similar observation was made in a group of low-income children aged 10 that had been exposed to cannabis in prenatal development.⁵

However, conflicting findings were observed in children of middle-class socioeconomic status exposed to prenatal marijuana use. Multiple studies found no issues relating to reading or language.⁶ ⁷

These mixed observations in children may suggest that the post-natal environment of a child can affect the long-term consequences of prenatal exposure to cannabis.

Can Smoking Weed Cause Low Birth Weight? 

Can Smoking Weed Cause Low Birth Weight?

Weight is an important unit of measurement as a child develops. Doctors will note weight changes to keep track of growth and be aware of potential problems in development.

A healthy newborn is generally between 5 pounds, 8 ounces, and 8 pounds 13 ounces. Premature babies usually have low birth weight and fall under 5 pounds 8 ounces. Babies higher in weight may be prone to issues like diabetes.⁸

Factors that can affect the size of a newborn include the size of the parents, the health of the mother and child, nutrition, gender, birth order, and cases of twins. 

Evidence is conflicting on whether or not cannabis use has an association with birth weight. 

A 2016 study concluded that, while cannabis use during pregnancy was often linked to low birth weight, cannabis was not an independent risk factor when looked at alongside the use of tobacco and other factors.⁹ 

In a study of 6468 women, 361 of which were marijuana users, researchers found that cannabis did not increase the risk of fetal anomalies but did increase the risk of low birth weight.¹⁰ The potential effect on birth weight may be related to the frequency of cannabis use, as women who reported “heavy use” (at least once weekly) had a higher chance of giving birth to an infant with a lower birth weight than women who reported “some use” (less than once weekly).

Can Smoking Weed Cause a Preterm Birth? 

A baby born before 37 weeks of pregnancy is considered preterm. Several factors can affect whether or not a baby is born preterm, including socioeconomic status, medical conditions, and behaviors like smoking, alcohol, or stress. Babies born preterm are subject to experiencing other medical conditions like cerebral palsy, vision and hearing impairments, and developmental delays.

A child can be born with a low birth weight but not be born premature, but a baby born prematurely most often will be born underweight. 

In the studies we reviewed, cannabis use alone was not associated with an increased risk of preterm birth, but it was when used in conjunction with tobacco. Given the currently available research, there is not enough evidence to prove conclusively whether cannabis usage alone causes premature birth. However, many doctors advise that smoking any substance while pregnant can present increased risks.

Can Smoking Weed Cause Stillbirth? 

More studies are needed to understand the relationship between smoking cannabis during pregnancy and cases of stillbirth. One study suggests a slight increase in the risk of stillbirth among cannabis users. However, the study could not be adjusted for tobacco use.¹¹

Smoking Weed vs Cigarettes While Pregnant 

Smoking Weed vs Cigarettes While Pregnant 

Cannabis and tobacco are a common mix for many consumers. In Europe, 77-90% of consumers combine the two.¹² However, despite the popularity of the combo, it carries along with it some risks.

Tobacco alone has more than 70 carcinogens, or chemicals known to increase the risk of cancer.¹³ And when combining cannabis and tobacco, the tobacco smoke is often unfiltered, which can increase the risk of developing physical and mental health issues.¹⁴

In the last few decades, there has been an abundance of research linking smoking tobacco and cigarettes during pregnancy to a wide range of risk factors for the fetus. According to the CDC, these risks include tissue damage to the lungs and brain and an increased risk of low birth weight.¹⁵ Tobacco use during pregnancy also has been linked to cases of ADHD.¹⁶

While the evidence is clear that prenatal exposure to smoke from tobacco has and can cause long-term health issues in children, it’s important to note that the inhalation of any substance is seen as harmful. Doctors do not advise smoking of any kind during pregnancy.

Is It Safe To Smoke Weed While Breastfeeding?

Breastfeeding is a natural feeding method between mother and child that supplies many important nutrients for development. According to the CDC, there isn’t enough data to declare whether or not it is safe to smoke weed while breastfeeding

However, a developing child is sensitive, and it’s generally recommended to limit any potential risk – including substances like alcohol and caffeine – to maintain the health of the breast milk supplied to the child.

Further research is needed to fully understand the effects of cannabis on breastfeeding.

Does Marijuana Affect Birth Control?

Depending on the type of birth control taken, cannabis use may cause side effects, but there is currently no evidence that cannabis use interferes with or weakens the effectiveness of birth control

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Current research studying the impact of cannabis on human pregnancy is limited and, at times, conflicting. While it is clear that smoking tobacco can cause adverse and long-term health effects to the child, more research is needed to understand how cannabis alone affects the developmental process. 

Since cannabis use can have adverse effects for some consumers, it is generally recommended that individuals refrain from cannabis use during pregnancy. And while there have been instances where cannabis use did not affect the pregnancy or health of the baby, it is not advised by doctors. 


¹ Mato, Susana, et al. “Ontogenetic Development of Cannabinoid Receptor Expression and Signal Transduction Functionality in the Human Brain.” European Journal of Neuroscience, vol. 17, no. 9, May 2003, pp. 1747–1754, 10.1046/j.1460-9568.2003.02599.x. Accessed 16 Feb. 2022.

² Biegon, Anat, and Ilan A. Kerman. “Autoradiographic Study of Pre- and Postnatal Distribution of Cannabinoid Receptors in Human Brain.” NeuroImage, vol. 14, no. 6, Dec. 2001, pp. 1463–1468, 10.1006/nimg.2001.0939. Accessed 26 Nov. 2020.

³ Willford, Jennifer A., et al. “Effects of Prenatal Tobacco, Alcohol and Marijuana Exposure on Processing Speed, Visual–Motor Coordination, and Interhemispheric Transfer.” Neurotoxicology and Teratology, vol. 32, no. 6, Nov. 2010, pp. 580–588, 10.1016/j.ntt.2010.06.004. Accessed 29 Mar. 2021.

⁴ Fried, P.A, and Barbara Watkinson. “Differential Effects on Facets of Attention in Adolescents Prenatally Exposed to Cigarettes and Marihuana.” Neurotoxicology and Teratology, vol. 23, no. 5, Sept. 2001, pp. 421–430, 10.1016/s0892-0362(01)00160-x. Accessed 24 Nov. 2020.

⁵ Goldschmidt, Lidush, et al. “Prenatal Marijuana and Alcohol Exposure and Academic Achievement at Age 10.” Neurotoxicology and Teratology, vol. 26, no. 4, July 2004, pp. 521–532, 10.1016/j.ntt.2004.04.003. Accessed 4 Apr. 2020.

⁶ Fried, Peter A., et al. “Reading and Language in 9- to 12-Year Olds Prenatally Exposed to Cigarettes and Marijuana.” Neurotoxicology and Teratology, vol. 19, no. 3, May 1997, pp. 171–183, 10.1016/s0892-0362(97)00015-9. Accessed 27 Jan. 2020.

⁷ Fried, P. A., et al. “60- and 72-Month Follow-up of Children Prenatally Exposed to Marijuana, Cigarettes, and Alcohol: Cognitive and Language Assessment.” Journal of Developmental and Behavioral Pediatrics: JDBP, vol. 13, no. 6, 1 Dec. 1992, pp. 383–391, pubmed.ncbi.nlm.nih.gov/1469105/. Accessed 1 Dec. 2022.

⁸ Desiraju, Madhu. “Your Newborn’s Growth (for Parents) - KidsHealth.” Kidshealth.org, 2018, kidshealth.org/en/parents/grownewborn.html.

⁹ Conner, Shayna N, et al. “Maternal Marijuana Use and Adverse Neonatal Outcomes: A Systematic Review and Meta-Analysis.” Obstetrics and Gynecology, vol. 128, no. 4, 2016, pp. 713–23, www.ncbi.nlm.nih.gov/pubmed/27607879, 10.1097/AOG.0000000000001649.

¹⁰ Warshak, C R, et al. “Association between Marijuana Use and Adverse Obstetrical and Neonatal Outcomes.” Journal of Perinatology, vol. 35, no. 12, 24 Sept. 2015, pp. 991–995, europepmc.org/abstract/MED/26401751, 10.1038/jp.2015.120. Accessed 7 Nov. 2019.

¹¹ ​​Varner, Michael W., et al. “Association between Stillbirth and Illicit Drug Use and Smoking during Pregnancy.” Obstetrics & Gynecology, vol. 123, no. 1, Jan. 2014, pp. 113–125, 10.1097/aog.0000000000000052.

¹² Global Overview and Highlights N > 115,000. 2017.

¹³ Canada, Health. “Carcinogens in Tobacco Smoke.” Www.canada.ca, 29 Mar. 2011, www.canada.ca/en/health-canada/services/publications/healthy-living/carcinogens-tobacco-smoke.html#:~:text=Key%20Messages. Accessed 1 Dec. 2022.

¹⁴ “Substance Use: Using Cannabis and Tobacco Together.” Myhealth.alberta.ca, myhealth.alberta.ca/Alberta/Pages/Using-cannabis-and-tobacco-together.aspx.

¹⁵ McGrath-Morrow, Sharon A., et al. “The Effects of Nicotine on Development.” Pediatrics, vol. 145, no. 3, 11 Feb. 2020, p. e20191346, 10.1542/peds.2019-1346.

¹⁶ Gustavson, Kristin, et al. “Smoking in Pregnancy and Child ADHD.” Pediatrics, vol. 139, no. 2, 30 Jan. 2017, p. e20162509, 10.1542/peds.2016-2509.

The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.

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