A new study published in JAMA Pediatrics suggests that children exposed to cannabis during pregnancy may be more likely to experience cognitive challenges by the time they reach preschool - particularly in areas related to executive functioning, like attention, emotional control, and flexible thinking.

What the Study Looked At

Researchers at Washington University in St. Louis analyzed data from over 350 mother-child pairs enrolled in a prospective birth cohort. All mothers were recruited during pregnancy and completed questionnaires about cannabis use at multiple points during gestation. Their children were followed up at preschool age (around 4 years old), when parents completed the Behavior Rating Inventory of Executive Function (BRIEF-P), a standardized tool used to evaluate early cognitive development.

Among participants, 43 mothers reported cannabis use during pregnancy. After adjusting for socioeconomic factors, maternal mental health, and other substance use, prenatal cannabis exposure was associated with significantly higher scores on measures of executive function difficulties - specifically in the areas of emotional regulation and inhibitory control.

What Executive Function Really Means

Executive function refers to a set of mental skills that help children manage their thoughts, actions, and emotions. It includes things like remembering instructions, resisting impulsive behavior, staying focused, and shifting attention when needed.

While many preschoolers have temporary struggles in these areas, consistent difficulties can interfere with learning, peer relationships, and self-regulation.

What This Means for Moms

This study doesn’t prove that cannabis use causes these problems - but it adds to a growing body of evidence suggesting prenatal exposure may carry subtle but meaningful risks to a child’s neurodevelopment.

One challenge is that cannabis is increasingly seen as a “natural” or even therapeutic product. In some states, it’s marketed to pregnant women as a remedy for morning sickness or anxiety. But THC, the main psychoactive compound in cannabis, crosses the placenta and interacts with the developing fetal brain - particularly in regions involved in cognition and emotion.

Because cannabis isn’t subject to FDA safety testing in pregnancy, the American College of Obstetricians and Gynecologists currently recommends avoiding its use altogether during pregnancy and lactation.

If You’re Pregnant or Trying to Conceive

• Talk openly with your OB or midwife about any cannabis use - no judgment.
• Don’t substitute cannabis for medical care. If you’re struggling with nausea, anxiety, or insomnia, safer options exist.
• If you used cannabis before learning you were pregnant, know that risk is often dose-dependent and outcomes vary. The best next step is to stop and focus on healthy prenatal care.

The Bottom Line

Not all kids exposed to cannabis in utero will have developmental problems - but emerging evidence suggests a heightened risk, especially in executive functioning. For expecting moms, this study adds another reason to err on the side of caution and seek alternatives that are known to be safe during pregnancy.

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Read the research:

• JAMA Pediatrics, 2024
• Center for Women’s Mental Health, MGH

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