Planning a baby often changes everyday choices, and cannabis deserves the same careful review as alcohol, nicotine, medications and other substances. Marijuana may be legal for adults, but legality does not make it harmless during the months when a pregnancy is planned or carried.
Major medical organizations recommend avoiding cannabis during pregnancy. The main psychoactive compound, delta-9-tetrahydrocannabinol (THC), can cross the placenta, and THC can also pass into breast milk. Cannabis smoke adds another source of potentially harmful chemicals.
If someone used cannabis before realizing they were pregnant, the useful next step is not panic or shame. Stop further exposure, tell the prenatal care provider what happened, and use that information to guide care.
What counts as cannabis use?
Marijuana, cannabis and weed are common names for products that may contain THC, CBD or both. People can smoke flower, vape, use concentrates, or take cannabis in edibles and drinks.
Changing the route does not make THC safe in pregnancy. The CDC specifically includes smoking, vaping, dabbing, eating and drinking cannabis among forms of exposure that may be harmful.
CBD should not be treated as an automatic exception. Products can contain THC, labels are not always perfectly reliable, and safety during pregnancy has not been established well enough to call CBD risk-free.
Why the pregnancy period matters
Pregnancy is a long process of growth and biological change. A developing fetus depends on the placenta and the pregnant person's bloodstream for oxygen and nutrients, which means substances circulating in the pregnant person's body can also create fetal exposure. ACOG's 2025 clinical consensus notes that cannabinoid receptors are present in the fetus early in development, and that THC can cross the placenta. The CDC likewise states that THC can pass through the pregnant person's system to the baby and may affect development.
This is one reason the idea of a "small amount" can be misleading. Medicine cannot promise that an occasional joint, one edible at a party or a few puffs is harmless. There is not an established safe level of cannabis use in pregnancy. Professional guidance therefore focuses on avoiding cannabis rather than trying to calculate a supposedly safe dose.
Researchers also have to account for the fact that cannabis use often occurs alongside other exposures and circumstances. Some people who use marijuana also smoke or vape nicotine, drink alcohol, use other drugs, take prescription medications, or live with stress, poverty, poor sleep or limited access to prenatal care. These factors can affect pregnancy outcomes too. Good studies try to adjust for them, but observational research cannot remove every uncertainty. The result is an evidence base that contains limitations, while still being strong enough for major organizations to recommend avoidance.
What has been linked to cannabis use in pregnancy?
The most consistent concerns are not that every exposed pregnancy will have a complication. Most definitely will not. The concern is that, across groups of pregnancies, prenatal cannabis exposure has been associated with higher rates of several adverse outcomes. ACOG's 2025 consensus highlights associations with spontaneous preterm birth, low birth weight, NICU admission and later neurocognitive or behavioral difficulties. The CDC similarly points to lower birth weight and concerns about neurological development.
Preterm birth
Preterm birth means a baby is born before 37 completed weeks of pregnancy. Premature babies are more likely to need specialized care and can face challenges related to breathing, feeding, temperature regulation and development. Cannabis exposure has been associated with spontaneous preterm birth in the medical literature, although researchers continue to study how much of the association is caused by cannabis itself and how much is connected to other factors that often occur with cannabis use.
Birth weight and fetal growth
Lower birth weight is another repeatedly reported concern. Fetal growth is influenced by many things, including genetics, placental function, nutrition, nicotine exposure and other health conditions. Even so, prenatal cannabis exposure has been associated in several studies with babies who weigh less at birth. This matters because babies who are born small or early can require closer monitoring after delivery.
Newborn and NICU care
Some studies have also found higher rates of newborn complications or neonatal intensive care admission among pregnancies exposed to cannabis. A NICU stay can be needed for many reasons, so it would be misleading to say cannabis causes every such admission. The more accurate point is that cannabis exposure has been associated with a greater chance of needing specialized newborn care in some populations.
Development and behavior
The questions that often worry parents most are the long-term ones. A child's brain continues developing rapidly before and after birth, and researchers are studying whether prenatal cannabinoid exposure can influence attention, learning, behavior and other aspects of neurodevelopment. ACOG reports associations between prenatal cannabis exposure and later neurocognitive or behavioral problems, while also recognizing that the evidence is affected by study limitations and potential confounding.
This distinction matters. A finding of association is not the same as proof that cannabis alone caused a particular child's later difficulty. It is also not accurate to say that one episode of use guarantees a developmental disorder. The responsible conclusion is narrower: prenatal cannabis exposure has been linked with outcomes that clinicians take seriously, and because a safe dose has not been established, avoidance is recommended.
Miscarriage, stillbirth and other outcomes
People often ask whether marijuana causes miscarriage or stillbirth. The research is less straightforward than the headlines sometimes suggest. Some studies have reported higher risks of pregnancy loss or stillbirth, while other studies have produced mixed findings. Because smoking, tobacco use and other exposures may occur at the same time, separating the independent effect of cannabis is difficult.
That uncertainty is not a reason to label cannabis safe. It is a reason to describe the evidence carefully. When a potential exposure has no established health benefit in pregnancy and credible studies raise concerns about fetal growth, premature delivery and development, medical organizations generally recommend choosing alternatives.
Does the way cannabis is used make a difference?
It is tempting to solve the problem by switching from smoking to vaping or edibles. That may change the pattern of exposure, but it does not create a pregnancy-safe form of THC. Smoking also adds toxic combustion products; edibles avoid smoke but can deliver substantial THC and have delayed effects.
For pregnancy planning, the simpler rule is more useful: if a product contains cannabis or THC, do not assume that the delivery method makes it safe.
What about cannabis used for nausea, pain, sleep or anxiety?
This is where a nonjudgmental conversation matters most. Some people use cannabis because they are trying to cope with real symptoms. Morning sickness, insomnia, chronic pain, anxiety and appetite changes can make pregnancy physically and emotionally exhausting. Telling someone to "just stop" without helping with the problem that led them to cannabis can leave them feeling dismissed.
ACOG's updated guidance specifically emphasizes asking why a patient is using cannabis and helping them identify safer ways to address the underlying issue. The goal is not simply to remove a substance; it is to replace the function that substance was serving when possible.
For example, severe nausea and vomiting may need medical evaluation and pregnancy-compatible treatment. Persistent anxiety may benefit from therapy, practical support, sleep strategies or medication when a clinician believes medication is appropriate. Pain deserves its own assessment rather than being managed with an unreviewed cannabis product. The right alternative depends on the person, the pregnancy and the reason the cannabis was being used.
Medical marijuana is still marijuana
A prescription, recommendation or medical-use status does not automatically make cannabis safe in pregnancy. ACOG advises people who are pregnant or planning pregnancy not to use marijuana, including medical marijuana, and encourages discussion of alternative treatments with a healthcare professional.
That can feel frustrating for someone who has been told by friends, social media or a dispensary that cannabis is a gentler option than another medicine. Pregnancy decisions should not be based on a simple "natural versus chemical" comparison. Plants contain active chemicals too, and the question in pregnancy is whether a treatment has been studied well enough, at an appropriate dose and for the specific condition, to understand its risks and benefits.
What about the parent who is trying to conceive?
Preconception is important because the healthiest pregnancy begins before the positive test. For the person who may become pregnant, stopping cannabis while trying to conceive avoids exposure during the early weeks of pregnancy, when someone may not know they are pregnant yet. ACOG's 2025 recommendations specifically include the prepregnancy period in screening and counseling.
For a male partner, the situation is somewhat different. The father or sperm-producing partner does not share the pregnant person's bloodstream with the fetus, so marijuana used by the male partner after conception is not expected to reach the fetus in the same way a pregnant person's use does. MotherToBaby notes that paternal exposures generally are not expected to increase the chance of birth defects because the amount of a substance reaching semen is usually too small to cause fetal exposure.
But that does not make marijuana irrelevant during family planning. Studies have reported changes in sperm count, concentration, shape or movement among some cannabis users, while other studies have found inconsistent or no clear effects on fertility. The American Society for Reproductive Medicine describes the evidence on marijuana and male or female fecundity as incomplete and conflicting.
For couples actively trying to conceive, this leads to a practical approach rather than a dramatic claim: the partner who may become pregnant should avoid cannabis, and both partners can discuss cannabis use with a healthcare professional if there are concerns about fertility or if stopping is difficult. Cutting out cannabis also removes uncertainty and makes it easier to build other healthy preconception habits together.
What if you used cannabis before you knew you were pregnant?
Finding out about a pregnancy after using cannabis is a reason to make a new decision, not to punish yourself for the past. Early pregnancy often passes before a person knows conception has happened.
The useful steps are simple: stop further use, tell the prenatal care provider what you used, how often, in what form, and when the last exposure occurred. That history helps the clinician interpret your overall pregnancy. Do not delay prenatal visits while worrying about how to explain an earlier exposure.
How to make stopping more realistic
Some people can stop immediately; others need support, especially when cannabis is tied to sleep, pain, stress or a daily routine. Start by removing products from easy reach, telling a partner what you are trying to change, and planning a substitute for the time when you normally use cannabis.
Look for the trigger behind the craving. Nighttime use may be linked to insomnia; daytime use may be a response to stress; use for nausea, pain or anxiety may point to a symptom that needs another treatment plan.
If stopping repeatedly does not work, involve a healthcare professional. Support is particularly useful when withdrawal symptoms, anxiety, sleep problems or other difficulties make a quit attempt hard to maintain.
Breastfeeding is another stage to discuss
The pregnancy ends at birth, but the cannabis conversation does not necessarily end there. THC is fat-soluble and can transfer into breast milk. MotherToBaby reports that THC can remain in breast milk for days or longer, and the exact duration varies with factors such as dose, frequency and individual metabolism. Because research on infant outcomes is still limited, major organizations advise avoiding marijuana while breastfeeding.
At the same time, ACOG's 2025 clinical consensus makes an important distinction: continued cannabis use is not a reason to discourage breastfeeding altogether. Breastfeeding has established health benefits, and the best plan for an individual family should be discussed with a healthcare professional. The goal is to stop cannabis use, support breastfeeding when appropriate, and avoid turning one risk conversation into an all-or-nothing judgment about parenting.
A simple plan for future parents
If you are planning a pregnancy, a practical checklist can be much more useful than memorizing every study. Review any cannabis, THC or CBD products in the home. Tell your healthcare provider what you use and why. If cannabis is helping with nausea, pain, sleep or anxiety, ask for alternatives before trying to stop on your own. Make the home smoke-free. If both partners use cannabis, talk openly about fertility, routines and the plan for stopping.
If pregnancy has already begun, the same basic steps apply, but with one extra priority: do not delay prenatal care while waiting until you have "cleaned everything up." Your clinician needs accurate information, not a perfect history.
And if you are the partner who is not carrying the pregnancy, do not assume that your own use is automatically a major fetal-exposure problem after conception. The evidence on paternal marijuana exposure and birth defects is reassuring in that specific respect, while research on sperm quality and fertility remains uncertain. A shared plan to reduce or stop cannabis before conception can still be reasonable, particularly for couples dealing with infertility or repeated difficulty conceiving.
The bottom line
Cannabis is sometimes described as a relatively gentle substance because it is legal, familiar and widely available. Pregnancy changes the question. The relevant issue is not whether cannabis feels mild compared with another drug; it is whether its benefits in pregnancy have been established strongly enough to outweigh potential risks to a developing baby. Major medical and public-health organizations do not consider cannabis a safe pregnancy treatment, and they recommend avoiding cannabis during pregnancy and while trying to conceive.
The evidence has limits, and responsible health writing should say so. Studies of cannabis in pregnancy are often observational and can be affected by tobacco use, dose, route, socioeconomic factors and other differences between people who use cannabis and those who do not. Those limitations mean we should avoid pretending that every reported outcome has been proven to be caused by cannabis alone. They do not create evidence of safety either.
For future parents, the most useful path is straightforward: avoid cannabis during pregnancy, avoid treating CBD or edible products as automatically safe, ask for help with the symptom or stress that made cannabis attractive in the first place, and tell your healthcare provider about past or current use without embarrassment. For partners who are not pregnant, fertility effects remain an area of ongoing research, so a conversation with a clinician is appropriate when conception is taking longer than expected or when cannabis use is frequent.
Changing course is worthwhile at any point. A positive pregnancy test does not erase what happened before it, but it gives you a clear opportunity to reduce future exposure and build a healthier plan for the months ahead.
Image sources
All four photographs used in this article are shared on Wikimedia Commons under CC0. Pregnant woman · Cannabis plant · Parents and their baby · Parent holding a baby's hand.
Medical references
- American College of Obstetricians and Gynecologists — Cannabis Use During Pregnancy and Lactation
- U.S. Centers for Disease Control and Prevention — Cannabis and Pregnancy
- Health Canada — Is cannabis safe during preconception, pregnancy and breastfeeding?
- American Society for Reproductive Medicine — Tobacco or marijuana use and infertility
This article is for general educational purposes and does not replace individualized medical advice. Recommendations can vary with a person’s health, medications, pregnancy and local care system.