Prenatal Cannabis Exposure Was Not Linked to Developmental Delays at Age 2

In 1,489 mother-infant dyads from the 3D prospective cohort, prenatal cannabis use (2.6% of women) showed no significant associations with cognitive (B=0.016), fine motor (B=0.029), gross motor (B=0.060), or language development (B=0.200) at age 2. An unexpected positive association between cannabis use and language development was found in girls only.

Data from 1,489 dyads in the 3D prospective pregnancy cohort (2010-2012). Prenatal cannabis use was measured via interviews each trimester. Child development was assessed using Bayley Scales of Infant and Toddler Development (BSID-III) for cognition and motor skills, and MacArthur-Bates Communicative Development Inventories for language at age 2. Multiple linear regressions with sex-stratified analyses were performed.

Concerns about prenatal cannabis effects on child development are widespread, but this large prospective study found no measurable impact at age 2. The use of clinician-administered developmental assessments rather than parent report strengthens the findings, though the majority of exposed women stopped after the first trimester.

This study adds to mixed evidence on prenatal cannabis effects. The lack of association at age 2 does not rule out later-emerging effects, as some neurodevelopmental impacts may not manifest until school age. The low prevalence of use and early cessation in most users may also limit the ability to detect effects of heavier or sustained exposure.

Self-reported cannabis use (no biomarker confirmation) likely underestimates true exposure. Only 2.6% reported use, limiting statistical power. Most users stopped after first trimester. Age 2 assessment may be too early to detect subtler cognitive effects. No measure of dose or potency.