Does cannabis use during pregnancy or breastfeeding cause harm?
Every major US medical body advises against cannabis during pregnancy and while breastfeeding. THC crosses the placenta and passes into breast milk, and studies tie exposure to low birth weight, preterm birth, stillbirth, and slower infant motor development. No safe amount, product type, or trimester window has been identified.
cannabis and pregnancy third trimester
- ACOG: recommends screening all pregnant patients for cannabis and counseling them to stop, and states there is not enough evidence to support cannabis for any pregnancy symptom.
- AAP: advises against marijuana use while pregnant or nursing and notes that THC is present in breast milk.
- CDC and FDA: recommend against use in pregnancy and lactation, and FDA has not approved any cannabis product for morning sickness.
These are position statements, not lab results. The advice is firm because fetal and infant exposure is measurable and the benefit side of the ledger is empty.
Cannabis and Pregnancy: A Comprehensive Review
How common is cannabis use during pregnancy?
CDC survey data puts past-month use near 5% among pregnant people aged 18 to 44, or about 1 in 20. Rates run higher in the first trimester, among younger adults, and in states with legal adult use. Many people stop once they learn they are pregnant, while others get advice from friends or forums instead of a clinician.
cannabis and pregnancy third trimester
What does the research link cannabis in pregnancy to?
Most human evidence is observational, so it cannot prove that cannabis alone caused an outcome. Use also tracks with tobacco, alcohol, income stress, and access to prenatal care, all of which shape birth outcomes. Even after researchers adjust for those factors, the direction of the findings holds.
Birth outcomes
- Lower birth weight, with the strongest signal in daily or heavy users.
- Higher rates of preterm birth and newborn intensive care admission.
- Stillbirth and placental complications reported in several large cohorts.
Brain and behavior
THC binds to cannabinoid receptors that help direct brain wiring before birth, which is why researchers watch this area. Children followed to school age show small differences in attention, memory, and impulse control after prenatal exposure. Effect sizes are modest and studies vary, but they point one way.
Secondhand smoke and vapor
Secondhand cannabis smoke carries many of the same irritants as tobacco smoke, plus THC. Household exposure is linked to low birth weight, wheezing, and higher SIDS risk in infants. Vaping removes some tar but not THC, and the aerosol still carries fine particles.
Does THC get into breast milk?
Yes. THC is fat soluble, so it collects in milk and in the infant's fat tissue. Lab tests have found THC in human milk for days after the last reported use, and in one small study the window ran to about six days. Metabolites of THC also show up in infant urine and stool, which confirms that a nursing baby absorbs it.
How much reaches the baby?
Nobody can give a number. Milk THC peaks about an hour after inhalation, then falls, but stored THC moves back into the blood for days. Edibles produce a later and longer peak than smoking. Because the dose depends on potency, frequency, body fat, and timing, "one hit" has no fixed value.
Can cannabis lower milk supply?
Some clinicians report reduced supply and slower letdown in heavy users, which may involve prolactin. The evidence is thin and rests on small studies and case reports. If supply is a concern, that is one more reason to stop.
Is CBD or a low-THC product safer during pregnancy?
No. CBD products sold online and in shops are not held to drug manufacturing standards, and testing has found THC in products labeled THC-free. CBD also blocks liver enzymes that clear other drugs, which can raise the level of medications you take. FDA has not approved CBD for nausea, pain, or anxiety in pregnancy.
Is cannabis a treatment for morning sickness?
No medical organization recommends it. ACOG points to proven options instead: vitamin B6 with doxylamine as a first step, and prescription drugs such as ondansetron or metoclopramide when symptoms are severe. Smoked cannabis adds carbon monoxide and tar to the exposure, which cuts oxygen flow to the fetus.
I used cannabis before I knew I was pregnant. What should I do?
Stop now and tell your prenatal provider. Quitting at any point in pregnancy lowers total exposure, and many people who stop in early pregnancy go on to have uncomplicated deliveries.
- Stop all cannabis products, including edibles, vapes, and topicals that contain THC.
- Tell your provider what you used, how much, and how often. Screening questions are for care planning, not punishment.
- Ask about approved treatments if nausea, anxiety, or sleep loss drove the use.
- Ask for a referral to counseling or a quit program if use is daily or hard to stop. The SAMHSA National Helpline is free at 1-800-662-4357.
Frequently asked questions
Can I pump and dump to clear THC from my milk?
No. THC sits in body fat and moves back into blood and milk for days, so pumping does not create a THC-free supply. Store-bought milk tests are not reliable enough to guide feeding decisions.
How long before conception should I stop using cannabis?
There is no evidence-based cutoff. Many clinicians suggest at least a month before trying to conceive, since THC can affect ovulation and sperm quality. Starting earlier gives more room.
Is marijuana safer than alcohol or tobacco during pregnancy?
No. All three are discouraged. Alcohol carries fetal alcohol spectrum risk, tobacco smoke raises low birth weight and SIDS risk, and cannabis adds its own neurodevelopmental concerns. Ranking them misses the point.
Does living in a legal state change the advice?
No. State law covers adult use and sales, not safety in pregnancy. Guidance from ACOG, AAP, CDC, and FDA applies in every state.
Bottom line
Cannabis and pregnancy breastfeeding guidance from every major US health agency says stop. THC reaches the fetus and the nursing infant, and no safe level has been found. If you are pregnant, nursing, or trying to conceive and you use cannabis, tell your provider and ask for help quitting. That conversation is the most useful step you can take.