A growing body of evidence links prenatal cannabis exposure to low birth weight, preterm birth, NICU admission, and later brain changes affecting memory, attention, and executive function—with THC potency rising from 5% to 30%.
Pregnant women considering cannabis use, obstetricians counseling patients, and neonatologists caring for exposed newborns.
What the researchers found
This review synthesizes the accumulating evidence on what happens when a developing fetus is exposed to cannabis—a question of increasing urgency as both cannabis use during pregnancy and THC potency rise simultaneously.
The pharmacological reality is concerning. THC crosses the placenta, disrupts the fetal endocannabinoid system that's critical for neurodevelopment, and accumulates in fetal tissues. For breastfeeding mothers, THC transfers into breast milk at approximately 2.5% of the maternal dose.
The clinical evidence has reached a critical mass. Multiple studies and meta-analyses now associate prenatal cannabis exposure with low birth weight, preterm birth, neonatal intensive care unit admission, and reduced Apgar scores. These aren't subtle statistical associations—they're clinically meaningful outcomes.
The neurodevelopmental data is perhaps most alarming. Longitudinal studies tracking exposed children over time have documented brain alterations affecting memory, attention, and executive function. These aren't just neonatal effects that resolve—they appear to be lasting changes in how the brain develops.
A crucial contextual factor: THC concentrations in cannabis products have risen dramatically, from roughly 5% to 30% over recent decades. A pregnant woman using cannabis today is exposing her fetus to far more THC than a woman using cannabis 20 years ago, yet much of the existing research was conducted with lower-potency products.
The ethical impossibility of randomized controlled trials in pregnant women means all evidence is observational, which limits causal conclusions. But the consistency and biological plausibility of the findings have strengthened the evidence base substantially.
Why it matters
Cannabis use during pregnancy is increasing precisely when it's becoming more dangerous—THC potency has multiplied while pregnant users often perceive cannabis as safer than pharmaceuticals or alcohol. The neurodevelopmental findings are particularly important because they suggest the effects extend far beyond the neonatal period, potentially affecting a child's cognitive trajectory for years.
The numbers in context
THC potency increase: ~5% to ~30%. THC crosses the placenta and accumulates in fetal tissues. Breastfed infants receive ~2.5% of maternal THC dose. Associated outcomes: low birth weight, preterm birth, NICU admission, reduced Apgar scores. Longitudinal evidence of brain alterations in memory, attention, and executive function.
How the study worked
Narrative review synthesizing observational studies, meta-analyses, and longitudinal cohort data on the effects of in-utero cannabis exposure on neonatal outcomes and child neurodevelopment.
Who was studied
Not enough information provided.
What this study cannot tell us
All evidence is observational—ethical constraints prevent randomized trials. Confounders (tobacco co-use, socioeconomic factors, polysubstance use) are difficult to fully control. Self-reported cannabis use during pregnancy likely underestimates true exposure. Most existing longitudinal studies used participants who consumed lower-potency cannabis than what's currently available. Animal studies help establish mechanisms but don't perfectly model human pregnancy.
How to read the evidence
Narrative review of observational evidence and meta-analyses—consistent findings with biological plausibility, but inherently limited by the inability to conduct randomized trials.
When this study was published
Published in 2025, synthesizing the current evidence base on prenatal cannabis exposure with attention to rising THC potency.
The bigger picture
This review connects to RTHC-00191's animal study showing timing-dependent effects of prenatal THC on amygdala development and social behavior, and to RTHC-00151's finding of reduced neonatal brain volume with prenatal cannabis exposure. The potency escalation (5% to 30%) links to the broader potency literature (RTHC-00162, RTHC-00106, RTHC-00115). As products get stronger, the fetal dose from the same pattern of maternal use increases substantially.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Are the neurodevelopmental effects worse with today's higher-potency products than what longitudinal studies captured? Is there a safe threshold of prenatal cannabis exposure, or any amount harmful? How should obstetric care address the rising rate of cannabis use during pregnancy?
Read the original research
Evidence on the effect of in-utero cannabis exposure in neonates.
Journal of perinatology : official journal of the California Perinatal Association, 45(11), 1503-1512
The Journal of Perinatology is a reputable source focusing on maternal and neonatal health.
Citation
Thayyil, Basel; Yusuf, Kamran. (2025). Evidence on the effect of in-utero cannabis exposure in neonates.. Journal of perinatology : official journal of the California Perinatal Association, 45(11), 1503-1512. https://doi.org/10.1038/s41372-025-02383-1
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