In a large cohort of over 10,000 pregnancies, prenatal cannabis exposure was associated with increased risk of communication delay at 12 months before adjusting for multiple comparisons, but no other developmental domains were affected.
Prenatal healthcare providers; researchers studying developmental effects of in-utero cannabis exposure.
Communication delay association: p = .02 before correction, not significant after
What the researchers found
Prenatal cannabis exposure was not associated with differences in gestational age or birth weight. It was significantly associated with increased risk of parent-reported developmental delay on the communication domain (p = .02), but this finding did not survive correction for multiple comparisons. No other ASQ-3 domains showed significant associations.
Why it matters
Cannabis use during pregnancy is increasing with legalization, and the developmental consequences remain unclear. This large study found limited evidence of harm at 12 months, with only a borderline signal for communication development that warrants monitoring but does not establish clear risk.
The numbers in context
Total sample: 10,695 pregnancies. ASQ-3 assessments: 3,742 infants at 12 months. Cannabis group differed significantly on all sociodemographic variables from non-users. Communication domain association: p = .02 before multiple comparison adjustment, not significant after. No significant associations with gestational age or birth weight (p > .05).
How the study worked
Prospective cohort from the Pregnancy During the COVID-19 Pandemic study (n = 10,695 total; n = 3,742 with 12-month ASQ-3 assessments). Propensity score weighting addressed demographic differences between cannabis-using and non-using groups. G-computations analyzed associations with birth outcomes and developmental delay.
What this study cannot tell us
The study was not specifically designed to examine prenatal cannabis effects. Cannabis use was self-reported and may be underreported. The ASQ-3 is a parent-report screening tool, not a comprehensive developmental assessment. Follow-up at 12 months may be too early to detect some developmental effects. The COVID-19 pandemic context may introduce unique confounders.
How to read the evidence
Moderate: large prospective cohort with propensity score weighting, but secondary analysis of a study not designed for this question, parent-reported outcomes, and self-reported exposure.
When this study was published
2024 study using 2021-2022 pandemic-era data.
The bigger picture
The question of prenatal cannabis safety is one of the most important and unsettled in perinatal research. This study joins a growing literature showing mixed results, with some subtle signals in communication and language development that may emerge more clearly at later ages when language demands increase.
Questions still open
- Would the communication delay signal strengthen at 18 or 24 months when language demands increase? Does the timing and amount of prenatal cannabis exposure affect developmental outcomes differently?
Common questions
Does this mean cannabis is safe during pregnancy?
Why did the communication finding not survive statistical correction?
Read the original research
Evaluation of the Association Between Prenatal Cannabis Use and Risk of Developmental Delay.
JAACAP open, 2(4), 250-262
Citation
Watts, Dana; Lebel, Catherine; Chaput, Kathleen; Giesbrecht, Gerald F; Dewsnap, Kyle; Baglot, Samantha L; Tomfohr-Madsen, Lianne. (2024). Evaluation of the Association Between Prenatal Cannabis Use and Risk of Developmental Delay.. JAACAP open, 2(4), 250-262. https://doi.org/10.1016/j.jaacop.2024.03.004
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