In 356,343 pregnancies, daily prenatal cannabis use was associated with 3.8 times greater odds of severe nausea and vomiting, challenging the common belief that cannabis helps with morning sickness.
Pregnant individuals using cannabis for nausea, OB-GYNs, midwives, and anyone advising on morning sickness management.
What the researchers found
Daily prenatal cannabis use was associated with 3.80x odds of severe NVP and 1.97x odds of mild NVP. Even preconception daily use predicted 2.61x odds of severe NVP, suggesting either reverse causation or that chronic use sensitizes the vomiting response.
Why it matters
Many pregnant individuals use cannabis specifically to treat morning sickness. This large study suggests the opposite — that cannabis use is associated with worse nausea and vomiting, possibly through a mechanism similar to cannabinoid hyperemesis syndrome.
The numbers in context
356,343 pregnancies. 11.3% preconception use, 6.5% prenatal use. 3.6% diagnosed with severe NVP, 16% mild NVP. Daily prenatal use: severe NVP aOR = 3.80 (95% CI: 3.28-4.39), mild NVP aOR = 1.97 (95% CI: 1.79-2.17).
How the study worked
Cross-sectional analysis of 356,343 pregnancies in Kaiser Permanente Northern California (2011-2022) with universal screening for cannabis use and ICD-coded NVP diagnoses.
What this study cannot tell us
Cross-sectional design cannot determine direction of causation — women with worse NVP may use more cannabis to cope. ICD codes may undercount NVP. Cannabis use frequency is self-reported.
How to read the evidence
Very large population study with universal screening, but cross-sectional design cannot establish causation — reverse causation is a significant concern.
When this study was published
Recent analysis spanning 2011-2022, providing the largest study to date on cannabis use and pregnancy nausea.
The bigger picture
The paradox of using cannabis for nausea while it may worsen nausea during pregnancy mirrors the CHS phenomenon. This challenges a widespread belief and has immediate clinical implications for prenatal counseling.
Questions still open
- Is cannabis causing worse NVP, or are women with worse NVP using more cannabis? Could the mechanism be related to cannabinoid hyperemesis syndrome?
Common questions
Does cannabis help with morning sickness?
Why would cannabis make nausea worse?
Read the original research
Frequency of Preconception and Prenatal Cannabis Use and Nausea and Vomiting in Pregnancy.
Obstetrics and gynecology, 145(5), 519-522
Citation
Young-Wolff, Kelly C; Chi, Felicia W; Campbell, Cynthia I; Alexeeff, Stacey E; Ansley, Deborah; Vanderziel, Alyssa; Lapham, Gwen T. (2025). Frequency of Preconception and Prenatal Cannabis Use and Nausea and Vomiting in Pregnancy.. Obstetrics and gynecology, 145(5), 519-522. https://doi.org/10.1097/AOG.0000000000005884
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