Marijuana During Pregnancy: What the Research Shows
Marijuana during pregnancy is now the most common illicit drug exposure in the womb, and the industry is part of the reason. THC crosses the placenta and shows up in breast milk for days. The largest review ever done, 51 studies and 21 million births, found higher odds of low birth weight, preterm birth and perinatal death. Dispensary staff recommend it for morning sickness anyway. Here is the evidence, what the medical bodies say, and what states should require.
Adjusted odds of harm with prenatal marijuana use
51 studies, 21.1 million pregnancies, versus no use
“Even after adjusting for co-use of tobacco products,” with confidence in the findings now rated moderate.
Use in pregnancy doubled, then jumped again when the stores opened
Past-month marijuana use among pregnant women, national survey
Use doubled between 2002 and 2017, with first-trimester use rising from 5.7 to 12.1 percent. In 2024, 5.0 percent of pregnant women reported past-month use, and 9.8 percent of pregnant 18 to 25 year olds. In a 2021 to 2023 analysis, 31 percent of pregnant users said a doctor had recommended it and 52 percent bought it at a dispensary.
U.S. Surgeon General, 2019 advisory (NSDUH 2002 to 2017); SAMHSA, 2024 NSDUH detailed tables; Wysota et al., Addictive Behaviors, 2026
Kaiser Permanente Northern California, 300,993 pregnancies
Screened by self-report plus urine test at eight to ten weeks. Use rose steadily for six years, then jumped the month California’s recreational stores opened. The increase appeared only in jurisdictions that allowed retail stores (RR 1.21) and not in those that banned them (RR 1.01). Among users in 2021 to 2022, 71 percent smoked, 33 percent used edibles, 22 percent vaped and 10 percent dabbed; those who dabbed were the most likely to use daily.
Young-Wolff et al., JAMA Health Forum, 2024; Young-Wolff et al., Drug and Alcohol Dependence, 2025
Retail stores do what retail stores do. The same commercialization effect runs through everything SAM has measured in legal states.
What happens to the pregnancy and the baby
Five meta-analyses and two national cohorts point the same direction. The effect sizes are moderate, consistent and dose-dependent.
| Outcome | Finding | Source |
|---|---|---|
| Low birth weight | Adjusted odds 1.75x (51 studies); 2.06x (16 studies); the Surgeon General cites a 50 percent higher risk | Lo 2025; Marchand 2022; Surgeon General |
| Preterm birth | 1.52x adjusted odds (51 studies) | Lo 2025 |
| Small for gestational age | 1.57x (51 studies); 1.47x with a dose-response effect (32 studies) | Lo 2025 |
| NICU admission | 1.38x (16 studies); 2.02x (24 studies) | Marchand 2022; Gunn 2016 |
| Perinatal death | 1.29x adjusted odds (low-certainty evidence) | Lo 2025 |
| Stillbirth | 2.34x odds with cord-blood evidence of use, partially confounded by smoking | NICHD Stillbirth Collaborative, 2014 |
| Neonatal morbidity or death | 14.1 percent vs 4.5 percent; adjusted odds 3.11x | Metz et al., AJOG, 2017 |
| Maternal complications | Gestational hypertension 1.17x, preeclampsia 1.08x, placental abruption 1.19x, 316,722 pregnancies | Young-Wolff et al., JAMA Internal Medicine, 2024 |
Odds ratios and relative risks are from observational studies adjusted for tobacco and other factors; they show association, not proof of cause, and the 2025 review rates its confidence as moderate.
THC reaches the fetus, and the effects show up years later
“Cannabinoid receptors are present in the fetus as early as 5 weeks. The main psychoactive component of cannabis, THC, is lipid-soluble, can cross the placenta, and can transfer into breast milk.”
American College of Obstetricians and Gynecologists, Clinical Consensus No. 10, October 2025
The fetal THC concentration runs about 10 percent of the mother’s, and “the risk of adverse outcomes increases in a dose-dependent fashion.” In breast milk, THC was detectable in 63 percent of samples up to about six days after the last use.
ACOG, Obstetrics and Gynecology, 2025; Bertrand et al., Pediatrics, 2018
Children at 9 to 11
In the 11,489-child ABCD study, prenatal exposure after the mother knew she was pregnant “remained associated with greater PLEs [psychotic-like experiences] and externalizing, attention, thought, and social problems.” The authors’ conclusion: “Cannabis use during pregnancy should be discouraged.”
Paul et al., JAMA Psychiatry, 2021
Autism: a contested finding
Across every Ontario birth over five years, autism was diagnosed at 4.00 per 1,000 person-years in exposed children versus 2.42 in unexposed, an adjusted hazard ratio of 1.51; the authors urged caution about residual confounding. A 2024 Kaiser cohort of 178,948 pregnancies found no association for early-pregnancy use. The honest summary is that the question is open, which is itself a reason not to expose a developing brain.
Corsi et al., Nature Medicine, 2020; Avalos et al., JAMA Network Open, 2024
Today’s products matter here. The research base was built on far weaker marijuana than the 20 percent flower and 70 percent concentrates sold now, and one in ten pregnant users in California dabs.
“Eight weeks pregnant with morning sickness.” Here is what the store said.
Colorado, 400 dispensaries, 2018
Medical-licensed dispensaries were the worst offenders, at 83 percent. The Surgeon General: “Alarmingly, many retail dispensaries recommend marijuana to pregnant women for morning sickness.”
Dickson et al., Obstetrics and Gynecology, 2018; U.S. Surgeon General, 2019
California, 505 budtenders, 2024 to 2025
Seven years and several state warning-label laws later, fewer than half of retail staff would tell a pregnant caller the product was unsafe, and almost none mentioned the warning the state requires them to post.
Why it works
About 70 percent of women, pregnant or not, believe weekly marijuana use carries slight or no risk. Among pregnant women who used in the past month, the share saying weekly use carries no risk at all rose from 26 percent in 2005 to 65 percent in 2015. An industry that sells “natural” and “wellness” is talking to customers who already believe it.
Every major medical authority says the same thing
“Obstetrician-gynecologists and other obstetric health care professionals should educate patients that there are no medical indications for cannabis use during pregnancy and the postpartum period.”
ACOG Clinical Consensus No. 10, October 2025
“No amount of marijuana use during pregnancy or adolescence is known to be safe.”
U.S. Surgeon General Jerome Adams, advisory, August 2019
“THC readily crosses the placenta and enters the rapidly developing brain of the fetus.”
American Academy of Pediatrics, 2018 clinical report release
The CDC: pregnant women should not use marijuana, and breastfeeding women “are encouraged to avoid all cannabis use,” because “THC is stored in body fat and is slowly released over time.” ACOG also advises against biologic testing as a screening tool and says continued use is not a reason to stop breastfeeding; the goal is cessation and care, not punishment.
Fathers too
In a prospective cohort of 1,535 couples, a male partner’s marijuana use once a week or more before conception was associated with twice the risk of miscarriage (adjusted hazard ratio 2.0), whether or not the woman used, and with higher risk for early losses and for men over 35.
Harlow et al., Epidemiology, 2021, Boston University PRESTO cohort
A warning on the wall is not a warning in the conversation
Washington requires every retailer to post a state pregnancy and breastfeeding sign at each point of sale; Colorado requires a posted warning that use “passes THC to your baby”; Michigan puts the warning on the label. An audit of five legal states found the required postings present in 65 percent of stores, and as low as 31 percent in Los Angeles. In California, 6 percent of budtenders mentioned a warning when a pregnant caller asked.
WAC 314-55-086; Berg et al., Addictive Behaviors, 2026; Young-Wolff et al., 2025
SAM’s asks
Warning labels on every product, not just a sign by the register, with the ACOG language: no medical indication for use in pregnancy.
Make it illegal for retail staff to give medical advice, with license penalties for recommending marijuana to pregnant customers, and audit compliance with callers the way researchers do.
Fund prenatal screening and treatment, by interview rather than drug testing, as ACOG recommends, so that women get care instead of a case file.
No “medical” marketing for nausea. Morning sickness has FDA-approved treatments. Marijuana is not one of them.
SAM model language and warning labels; SAM on Maternal Health Awareness Day, 2026
Marijuana during pregnancy: common questions
Is it safe to use marijuana during pregnancy?
No. The American College of Obstetricians and Gynecologists says there are no medical indications for marijuana use in pregnancy or the postpartum period, and the Surgeon General says no amount is known to be safe. THC crosses the placenta, and a 2025 review of 51 studies covering 21 million pregnancies found 1.75 times the adjusted odds of low birth weight, 1.52 times the odds of preterm birth and 1.29 times the odds of perinatal death.
Can marijuana help with morning sickness?
There is no evidence it is safe or effective for that, and ACOG says there are no medical indications for marijuana in pregnancy. Heavy use can itself cause cannabinoid hyperemesis syndrome, a cycle of severe vomiting. Yet 69 percent of Colorado dispensaries recommended marijuana to a caller describing morning sickness, which is why FDA-approved treatments exist and dispensary staff should not be giving medical advice.
Does THC pass to the baby?
Yes. THC is fat-soluble, crosses the placenta, and reaches the fetus at roughly 10 percent of the mother’s concentration; cannabinoid receptors are present in the fetus from five weeks. After birth, THC was detectable in breast milk up to about six days after the last use in a Pediatrics study.
What are the effects of marijuana on the baby?
Higher odds of low birth weight, preterm birth, small size for gestational age and NICU admission, and in some studies stillbirth and perinatal death. In a study of 11,489 children aged 9 to 11, prenatal exposure after the mother knew she was pregnant was associated with more psychotic-like experiences and attention, thought and social problems. An autism link has been found in one large study and not in another.
How many pregnant women use marijuana?
About 1 in 20. In the 2024 federal survey, 5.0 percent of pregnant women aged 15 to 44 reported past-month use, and 9.8 percent of pregnant 18 to 25 year olds. Use roughly doubled between 2002 and 2017, and in California it jumped the month recreational stores opened, but only where retail was allowed.
Does a father’s marijuana use matter?
It appears to. In a prospective study of 1,535 couples, a male partner’s use once a week or more before conception was associated with twice the risk of miscarriage, independent of the woman’s use.
Related: Marijuana myths and facts · Marijuana and mental health · Youth marijuana use · Marijuana deaths · Marijuana potency
The doctors agree. The dispensaries do not care.
Every major medical body says no marijuana in pregnancy. The stores selling it say otherwise. SAM has the warning-label language and the model rules for your state.
