In utero cannabis exposure linked to low birth weight and preterm birth in large study
Among nearly 365,000 infants, in utero cannabis exposure was associated with 20% higher odds of low birth weight and 24% higher odds of small for gestational age, with dose-response relationships for these outcomes.
Quick Facts
What This Study Found
After adjustment, in utero cannabis exposure was associated with low birth weight (aOR 1.20, 95% CI 1.12-1.28), small for gestational age (aOR 1.24, 95% CI 1.18-1.30), preterm birth <37 weeks (aOR 1.06, 95% CI 1.00-1.13), and NICU admission (aOR 1.06, 95% CI 1.01-1.11). Dose-response for low birth weight and SGA with increasing use frequency.
Key Numbers
364,924 infants, 22,624 (6.2%) cannabis-exposed. Low birth weight aOR: 1.20 (1.12-1.28). SGA aOR: 1.24 (1.18-1.30). Preterm <37 weeks aOR: 1.06 (1.00-1.13). NICU aOR: 1.06 (1.01-1.11). Early preterm <34 weeks aOR: 1.11 (1.00-1.23, p=0.055).
How They Did This
Population-based retrospective cohort of 364,924 singleton births at Kaiser Permanente Northern California (2011-2020). Cannabis exposure defined by self-report and/or positive urine toxicology. Models adjusted for demographics, other substance use, comorbidities, and prenatal care adequacy.
Why This Research Matters
This is one of the largest studies examining cannabis and neonatal outcomes. The dose-response relationship for birth weight and SGA strengthens the evidence that cannabis exposure, not just confounding factors, contributes to these outcomes.
The Bigger Picture
The consistent finding of dose-response relationships across multiple studies and populations builds a compelling case that prenatal cannabis use has real, if modest, effects on fetal growth. The 6.2% exposure rate means a substantial number of pregnancies are affected.
What This Study Doesn't Tell Us
Observational design cannot prove causation. Cannabis use may be underreported. Cannot separate effects of smoking cannabis from THC itself. Some outcomes (preterm, NICU) had borderline significance.
Questions This Raises
- ?Do different routes of cannabis administration (smoking vs. edibles) produce different neonatal risks?
- ?Is the birth weight effect clinically meaningful for individual infants?
Trust & Context
- Key Stat:
- 6.2% of pregnancies exposed
- Evidence Grade:
- Very large population-based cohort with objective exposure measurement, confounder adjustment, and dose-response analysis provides strong evidence.
- Study Age:
- 2024 study of Kaiser Permanente data from 2011-2020
- Original Title:
- Neonatal outcomes associated with in utero cannabis exposure: a population-based retrospective cohort study.
- Published In:
- American journal of obstetrics and gynecology, 231(1), 132.e1-132.e13 (2024)
- Authors:
- Avalos, Lyndsay A(13), Adams, Sara R(18), Alexeeff, Stacey E(19), Oberman, Nina R, Does, Monique B, Ansley, Deborah, Goler, Nancy, Padon, Alisa A, Silver, Lynn D, Young-Wolff, Kelly C
- Database ID:
- RTHC-05100
Evidence Hierarchy
Frequently Asked Questions
How much does cannabis affect birth weight?
Cannabis exposure was associated with 20% higher odds of low birth weight and 24% higher odds of being small for gestational age. The risk increased with more frequent use, supporting a dose-response relationship.
Were these effects independent of other substance use?
Yes. The analysis adjusted for other prenatal substance use, and sensitivity analyses further supported the associations, though some outcomes like preterm birth had borderline significance.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05100APA
Avalos, Lyndsay A; Adams, Sara R; Alexeeff, Stacey E; Oberman, Nina R; Does, Monique B; Ansley, Deborah; Goler, Nancy; Padon, Alisa A; Silver, Lynn D; Young-Wolff, Kelly C. (2024). Neonatal outcomes associated with in utero cannabis exposure: a population-based retrospective cohort study.. American journal of obstetrics and gynecology, 231(1), 132.e1-132.e13. https://doi.org/10.1016/j.ajog.2023.11.1232
MLA
Avalos, Lyndsay A, et al. "Neonatal outcomes associated with in utero cannabis exposure: a population-based retrospective cohort study.." American journal of obstetrics and gynecology, 2024. https://doi.org/10.1016/j.ajog.2023.11.1232
RethinkTHC
RethinkTHC Research Database. "Neonatal outcomes associated with in utero cannabis exposure..." RTHC-05100. Retrieved from https://rethinkthc.com/research/avalos-2024-neonatal-outcomes-associated-with
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.