Longitudinal Associations Between Cannabis Use during Pregnancy and Child Cognitive, Motor, and Language Development at 2 Years Old.

Objectives: The objectives of this study are to describe cannabis use during pregnancy, identify associated factors, examine the associations between prenatal cannabis use and the cognitive, motor and language development of 2-year-old children, and determine whether these associations differ according to child sex.

Methods: Data from 1489 mother-infant dyads from the 3D prospective pregnancy and birth cohort Study (2010-2012) were used. Prenatal cannabis use was measured during interviews in each trimester of pregnancy. Cognitive and motor development were assessed by The Bayley Scales of Infant and Toddler Development (BSID-III) and language development by the MacArthur-Bates Communicative Development Inventories at 2 years of age. Multiple linear regressions and differential analyses by child sex were performed.

Results: 2.6% of women reported using cannabis during pregnancy, the majority of whom stopped after the first trimester. Prenatal cannabis use was associated with lower socioeconomic status, prenatal use of alcohol and tobacco, and more distress symptoms during the first trimester of pregnancy. Results showed no significant associations between prenatal cannabis use (yes/no) and developmental indicators (Cognitive: B = 0.016, 95% CI [-0.268, 0.299]; Fine motor: B = 0.029, 95% CI [-0.271, 0.328]; Gross motor: B = 0.060, 95% CI [-0.143, 0.544]; Language: B = 0.200, 95% CI [-0.229, 0,465]). Contrary to our hypothesis, a positive association between cannabis use and language development was found in girls only.

Conclusion: The study, consisting of a large sample and developmental indicators independent of parental assessment, highlights the need for more studies on prenatal cannabis exposure documented by biomarkers.