Adding Cannabis to Alcohol During Pregnancy Increases Risk of Small Babies
Among pregnancies with alcohol diagnoses, co-occurring cannabis use was associated with 21% higher risk of small-for-gestational-age infants, while adding tobacco raised preterm birth risk by 44%.
Quick Facts
What This Study Found
Compared to alcohol alone, co-occurring alcohol+cannabis increased SGA risk (aRR=1.21); alcohol+tobacco increased extreme/very preterm birth (aRR=1.44), late preterm (aRR=1.25), and SGA (aRR=1.31); all three substances had the highest extreme preterm risk (aRR=1.68).
Key Numbers
California births 2007-2021; alcohol+tobacco: aRR=1.44 extreme/very PTB, 1.25 late PTB, 1.31 SGA; alcohol+cannabis: aRR=1.21 SGA; all three: aRR=1.68 extreme/very PTB, 1.29 SGA.
How They Did This
Population-based retrospective cohort linking California birth certificates (2007-2021) to maternal/infant hospitalization records, using ICD-9/10 codes for substance use diagnoses with adjusted risk ratio analysis.
Why This Research Matters
This is one of the first large studies to isolate cannabis's additive effect on birth outcomes beyond alcohol — showing that polysubstance use compounds risk in measurable, clinically significant ways.
The Bigger Picture
Prenatal substance use rarely involves just one substance — understanding how combinations multiply risk is essential for targeted screening and intervention during pregnancy.
What This Study Doesn't Tell Us
ICD codes may undercount substance use; cannot determine dose, timing, or frequency; California-specific population; unmeasured confounders possible despite adjustment.
Questions This Raises
- ?Does cannabis alone (without alcohol) carry similar SGA risk?
- ?At what gestational period is polysubstance exposure most harmful?
Trust & Context
- Key Stat:
- Evidence Grade:
- Large population-based cohort using 15 years of linked administrative data with adjusted analyses, though limited by ICD-based exposure ascertainment.
- Study Age:
- Published in 2026 with 2007-2021 California data, spanning both pre- and post-legalization periods.
- Original Title:
- Adverse birth outcomes in alcohol-exposed pregnancies with or without tobacco and cannabis.
- Published In:
- Preventive medicine, 202, 108427 (2026)
- Authors:
- Anunziata, Florencia, Frankeberger, Jessica(2), Baer, Rebecca J(4), Chambers, Christina, Bandoli, Gretchen
- Database ID:
- RTHC-08086
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Does cannabis make alcohol more dangerous during pregnancy?
Yes — this study found that adding cannabis to alcohol during pregnancy increased the risk of having a small-for-gestational-age baby by 21%, and adding tobacco made risks even higher.
Which substance combination is most risky during pregnancy?
All three together (alcohol, tobacco, and cannabis) carried the highest risk — 68% increased risk of extreme preterm birth compared to alcohol alone.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-08086APA
Anunziata, Florencia; Frankeberger, Jessica; Baer, Rebecca J; Chambers, Christina; Bandoli, Gretchen. (2026). Adverse birth outcomes in alcohol-exposed pregnancies with or without tobacco and cannabis.. Preventive medicine, 202, 108427. https://doi.org/10.1016/j.ypmed.2025.108427
MLA
Anunziata, Florencia, et al. "Adverse birth outcomes in alcohol-exposed pregnancies with or without tobacco and cannabis.." Preventive medicine, 2026. https://doi.org/10.1016/j.ypmed.2025.108427
RethinkTHC
RethinkTHC Research Database. "Adverse birth outcomes in alcohol-exposed pregnancies with o..." RTHC-08086. Retrieved from https://rethinkthc.com/research/anunziata-2026-adverse-birth-outcomes-in
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.