Cannabis and Pregnancy: What the Science Actually Says

Why This Conversation Matters More Than Ever

Here’s a number that might surprise you: according to a 2019 study published in JAMA, cannabis use among pregnant individuals in the United States nearly doubled between 2002 and 2017, rising from approximately 3.4% to 7% [Volkow et al., 2019]. Among those in their first trimester, the rate climbed even higher — to roughly 12%.

At the same time, the legal landscape around cannabis has shifted dramatically. With more states legalizing adult-use cannabis and an expanding wellness market promoting cannabinoids for nausea, anxiety, and sleep, many expecting parents find themselves navigating a confusing gap between cultural normalization and medical guidance.

This isn’t a simple topic, and it deserves more than a simple “just say no.” It deserves honest, evidence-based information.

So let’s be crystal clear about what this article is — and what it isn’t. This is not medical advice. This is a comprehensive look at what the current body of research tells us about cannabis exposure during pregnancy and early development. The goal is to help you understand the science so you can have informed, empowered conversations with your healthcare provider.

Important disclaimer: If you are pregnant, planning to become pregnant, or breastfeeding, please consult your OB-GYN, midwife, or other qualified healthcare provider before using any cannabis products. Major medical organizations — including the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), and the World Health Organization (WHO) — currently recommend against cannabis use during pregnancy and lactation.

By the end of this article, you’ll understand how cannabis interacts with fetal development at a biological level, what the research has (and hasn’t) established, and why this area of science is so genuinely complex.

Let’s get into it.

The Science Explained

The Endocannabinoid System and Fetal Development

To understand why researchers are concerned about prenatal cannabis exposure, you first need to understand a remarkable system already at work inside every human body — including a developing fetus.

The endocannabinoid system (ECS) is a vast cell-signaling network that plays a critical role in regulating mood, appetite, pain, immune function, and — crucially — neurodevelopment. Think of the ECS as a master dimmer switch for your nervous system. It doesn’t create signals so much as it fine-tunes them, helping your brain and body maintain balance (a concept scientists call homeostasis).

The ECS has three main components:

• Endocannabinoids — molecules your body produces naturally (like anandamide and 2-AG) that are structurally similar to the cannabinoids found in the cannabis plant
• Receptors — primarily CB1 receptors (concentrated in the brain and nervous system) and CB2 receptors (found mostly in immune cells)
• Enzymes — proteins that break down endocannabinoids after they’ve done their job

Here’s the key insight: the ECS is active incredibly early in fetal development. CB1 receptors have been detected in the human fetal brain as early as 14 weeks of gestation [Zurolo et al., 2021]. These receptors aren’t just passively sitting there — they’re actively guiding critical processes like neural proliferation (the creation of new brain cells), neuronal migration (brain cells moving to the correct locations), and synaptogenesis (the formation of connections between brain cells) [Harkany et al., 2007].

Imagine building a house. The ECS is like the construction foreman, directing workers (neurons) to the right rooms, making sure the wiring (synapses) gets connected properly, and ensuring the whole structure is sound. Endocannabinoids like anandamide serve as the foreman’s instructions.

Now, when THC (delta-9-tetrahydrocannabinol) — the primary psychoactive compound in cannabis — enters the body, it binds to those same CB1 receptors. It essentially mimics the foreman’s voice, but with different instructions. During a critical developmental window, this interference may disrupt the precisely timed signaling that guides healthy brain formation [Alpár et al., 2016].

CBD (cannabidiol) interacts with the ECS differently — it doesn’t bind strongly to CB1 or CB2 receptors — but it does influence the system indirectly, and research on its effects during pregnancy is even more limited than research on THC.

What the Research Shows

Let’s look at what the science has actually found, while being honest about its limitations.

Animal Studies

Much of what we know about the biological mechanisms comes from animal research, which allows for controlled conditions impossible in human studies.

• A landmark review by Harkany et al. (2007) demonstrated that prenatal THC exposure in rodents disrupted the development of the dopamine and glutamate neurotransmitter systems — both essential for learning, motivation, and emotional regulation.
• Research in rats has shown that prenatal cannabinoid exposure can alter the structure and function of the prefrontal cortex, a brain region critical for decision-making and impulse control [Tortoriello et al., 2014].
• Animal studies also suggest that prenatal THC exposure may make offspring more vulnerable to substance use later in life, a concept researchers call cross-sensitization [DiNieri et al., 2011].

Important caveat: Animal studies use controlled doses and standardized conditions. Results don’t always translate directly to humans, but they help us understand potential biological pathways.

Human Observational Studies

Human research on cannabis and pregnancy is challenging for ethical and practical reasons — you can’t design a randomized controlled trial asking pregnant people to use cannabis. So researchers rely on observational studies, which track outcomes in people who self-report cannabis use. These studies have inherent limitations, including:

• Self-reporting bias (people may underreport use due to stigma)
• Confounding factors (cannabis users may also use tobacco, alcohol, or have different socioeconomic circumstances)
• Varying potency (today’s cannabis products are dramatically stronger than those available in earlier decades)

With those caveats clearly stated, here’s what the observational data suggests:

Birth outcomes: A meta-analysis by Gunn et al. (2016) found that cannabis use during pregnancy was associated with a 36% increase in the likelihood of low birth weight and a modest increase in preterm birth risk. However, the researchers noted difficulty fully controlling for concurrent tobacco use.

Childhood development: The Ottawa Prenatal Prospective Study (OPPS) and the Maternal Health Practices and Child Development Study (MHPCD) — two of the longest-running longitudinal studies — have followed children exposed to prenatal cannabis into adulthood. Findings suggest subtle but measurable effects on:

• Executive function (planning, attention, impulse control) [Fried & Watkinson, 2000]
• Academic performance, particularly in reading and spelling tasks [Goldschmidt et al., 2004]
• Increased impulsivity and hyperactivity in some assessments during childhood [Day et al., 1994]

The word subtle matters here. These studies did not find dramatic cognitive impairments, but they did identify patterns of difficulty in higher-order thinking skills — the kind that become more important as children grow older and face more complex academic and social challenges.

Emerging research: The ongoing Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term study of brain development in the United States, is beginning to provide new data on prenatal cannabis exposure. Early findings have identified differences in brain structure among exposed children, though researchers caution that it’s too early to draw definitive conclusions [Paul et al., 2021].

What About CBD Products?

This is one of the most common questions expecting parents ask, and unfortunately, the honest answer is: we don’t have enough data.

CBD has been widely marketed as a non-psychoactive wellness compound, and many people assume it’s inherently safe. But “non-psychoactive” does not mean “no biological activity.” CBD influences serotonin receptors, TRPV1 ion channels, and — importantly — the metabolism of endocannabinoids through enzyme inhibition [Bisogno et al., 2001].

Very few studies have specifically examined CBD use during pregnancy. A 2020 review in Frontiers in Pharmacology noted that while CBD shows lower toxicity than THC in many contexts, its effects on fetal development remain “largely unexplored” and cannot be assumed safe [Pertwee, 2020].

Additionally, the CBD market remains poorly regulated. Independent testing has repeatedly found that many commercial CBD products contain:

• More THC than labeled
• Contaminants such as heavy metals and pesticides
• Inaccurate CBD concentrations

For these reasons, ACOG and the FDA both recommend against CBD use during pregnancy.

Cannabis and Breastfeeding

THC is lipophilic — meaning it dissolves in fat. Breast milk is high in fat. This means THC readily transfers into breast milk and can remain detectable for extended periods.

A study by Baker et al. (2018) found that THC was detectable in 63% of breast milk samples from cannabis-using mothers, with some samples testing positive up to six days after last use. The developing infant’s brain remains highly plastic during breastfeeding, and CB1 receptors continue to play a role in neurodevelopment throughout infancy.

Research on the specific effects of THC exposure through breast milk is limited, but the biological plausibility for concern is strong enough that the AAP recommends abstaining from cannabis during breastfeeding [Garry et al., 2009].

Why Morning Sickness Makes This Complicated

Here’s the human reality behind the statistics: hyperemesis gravidarum — severe, persistent nausea and vomiting during pregnancy — affects up to 2% of pregnant individuals and can be genuinely debilitating. Standard anti-nausea medications don’t always work, and some carry their own risks.

Cannabis has well-documented antiemetic (anti-nausea) properties, primarily through THC’s action on CB1 receptors in the brainstem’s vomiting center. It’s understandable why some people turn to it when they’re unable to keep food or water down.

This is precisely the kind of situation that demands an open, non-judgmental conversation with a healthcare provider rather than self-medication. Providers may be able to offer alternative treatments, adjust dosing of existing medications, or provide closer monitoring if a patient discloses cannabis use.

If you’re struggling with severe nausea during pregnancy, please reach out to your healthcare team. You deserve support, not stigma.

Practical Implications

What This Means for You

The science, while imperfect, points in a consistent direction: prenatal cannabis exposure carries potential risks to fetal neurodevelopment that are not yet fully understood. The precautionary principle — the idea that when the stakes are high and the evidence suggests possible harm, caution is warranted — applies here.

Here’s what this looks like in practice:

1. If you’re planning to become pregnant, consider tapering off cannabis use before conception. THC is stored in fat cells and can remain in the body for weeks. Giving your body time to clear stored cannabinoids is a reasonable precaution.

2. If you discover you’re pregnant and have been using cannabis, don’t panic. The research describes population-level statistical associations, not guaranteed outcomes. Talk to your provider honestly — they need accurate information to give you the best care.

3. If you’re using cannabis for a medical condition (chronic pain, PTSD, epilepsy, anxiety), work with your healthcare team to explore pregnancy-safe alternatives. Abruptly stopping a medication — including cannabis — can sometimes carry its own risks.

4. If you’re breastfeeding, be aware that THC transfers into breast milk and that “pump and dump” strategies (discarding milk after use) are not reliable for clearing THC the way they might be for alcohol, due to THC’s fat-soluble nature and long half-life.

5. Be skeptical of anyone who tells you cannabis is “totally safe” during pregnancy. The evidence doesn’t support that claim. Equally, be skeptical of anyone who shames or judges you without offering constructive support.

A Note on the High Families and This Topic

Our High Families system is designed to help you find the right cannabis experience for your needs — whether that’s an Uplifting High for social energy or a Relaxing High for winding down. But this is one area where no High Family is recommended during pregnancy or breastfeeding. The potential risks apply across all cannabis products, regardless of terpene profile, cannabinoid ratio, or method of consumption.

When the time is right — after pregnancy and breastfeeding — the High Families system will be here to help you rediscover what works best for you.

Key Takeaways

• The endocannabinoid system is active early in fetal development, and THC can interfere with the precisely timed signaling that guides brain formation.
• Human observational studies suggest associations between prenatal cannabis use and subtle effects on executive function, attention, and academic performance in children — though confounding factors make definitive conclusions difficult.
• CBD is not proven safe during pregnancy. Limited research and poor product regulation mean it cannot be assumed risk-free.
• THC transfers readily into breast milk and can remain detectable for days after use.
• Every major medical organization currently recommends against cannabis use during pregnancy and breastfeeding. Open, honest conversations with healthcare providers are the best path forward.

FAQs

Is using cannabis once or twice early in pregnancy dangerous?

The research focuses on patterns of regular use rather than isolated exposures. A single use is unlikely to cause dramatic harm, but the science can’t give a precise “safe threshold.” If you used cannabis before knowing you were pregnant, discuss it with your provider — the goal is information, not judgment.

Are edibles safer than smoking during pregnancy?

Smoking introduces combustion byproducts (carbon monoxide, tar) that are independently harmful during pregnancy. However, edibles still deliver THC into the bloodstream and across the placental barrier. The route of administration changes some risks but doesn’t eliminate the core concern about THC exposure to the developing fetus.

What about topical cannabis products?

Topical creams and balms are generally designed to act locally without significant systemic absorption. However, transdermal patches and some formulations are designed for systemic delivery. The research on topical cannabis use during pregnancy is virtually nonexistent, so caution is warranted. Discuss specific products with your healthcare provider.

Will my doctor report me if I tell them I use cannabis?

Laws vary significantly by state and country. In most U.S. states, healthcare providers are not required to report cannabis use by pregnant patients, and many providers actively encourage honest disclosure to provide better care. However, some states do have mandatory reporting laws, particularly if drug testing occurs at