Fetal exposure to cannabis, neonatal adiposity, and postnatal growth trajectories: The Healthy Start study

Abstract

Objective: Cannabis use during pregnancy is associated with lower birth weight and may influence postnatal growth. We estimated associations of fetal exposure to cannabis with neonatal adiposity and body mass index (BMI) z-score trajectories through age 3 years, as well as effect modification by breastfeeding. Methods: We leveraged a subsample of 130 mother-child pairs from a Colorado-based cohort. Twelve cannabinoids/metabolites (including delta 9-tetrahydrocannabinol [THC] and cannabidiol [CBD]) were measured in maternal urine collected at ~27 weeks gestation. Fetal exposure to cannabis was dichotomized as exposed (any cannabinoid≥limit of quantification) and not exposed (cannabinoids<limit of quantification). Generalized linear models estimated the associations between fetal exposure to cannabis with birth weight and neonatal adiposity (measured by air displacement plethysmography). A mixed-effects model estimated the association between fetal cannabis exposure and BMI z-score trajectories. Interaction by breastfeeding duration was assessed by including a product term (with fetal exposure to cannabis) in a mixed-effects model. Results: Fetal exposure to cannabis was associated with lower birth weight (-206g; 95% CI: -393, -18; p=0.03) and neonatal adiposity (-2.0%; 95% CI: -3.7, -0.02; p=0.03) followed by rapid postnatal growth through 3 years (0.37 increase in BMI z-score per square root year; 95% CI: 0.01, 0.60; p=0.02). Breastfeeding modified this association (p for interaction<0.01). Among cannabis-exposed offspring who were not breastfed, BMI z-scores were 0.42 lower at 6 months (95% CI: -1.15, 0.31) but 0.54 higher at 36 months (95% CI: -0.36, 1.44). Conversely, BMI z-scores were no different by fetal cannabis exposure among offspring who were breastfed for ~5 months. Conclusions: Our data suggests that fetal exposure to cannabis alters fetal and postnatal growth, and that breastfeeding may stabilize over-compensatory growth among cannabis-exposed offspring. Although the impact of lactational exposure to cannabis requires further investigation, it remains important to caution against cannabis use during pregnancy and lactation.