Cannabis linked to lower birth weight in new pregnancy study

To estimate associations of more than minimal prenatal nicotine, alcohol, cannabis, and opioid exposures with gestational age, birth weight, and birth weight for gestational age. Data were drawn from the HEALthy Brain and Child Development (HBCD) Study, a multisite, longitudinal study in the United States. Predefined recruitment thresholds for each substance were assessed using maternal self-report, maternal toxicology results, and newborn substance exposure-related diagnoses. Birth outcomes included gestational age at delivery (weeks), birth weight (grams), and birth weight for gestational age (centiles). Mean differences and risk ratios for the associations between substance exposure and birth outcomes were estimated using multilevel mixed-effect linear regression or multilevel mixed-effect Poisson regression. Among 660 mother-infant dyads, 17% (n = 115) of participants met recruitment thresholds for prenatal cannabis, 15% for nicotine (n = 102), 13% for alcohol (n = 86), and 5% for opioids (n = 32). In adjusted models, prenatal cannabis and opioid exposures were each associated with lower birth weight (cannabis: -272.2 [95% CI -444.6 to -99.8] g; opioids: -295.4 [95% CI -574.9 to -15.9] g) and birth weight centiles (cannabis: -8.2 [95% CI -15.3 to -1.1] centiles; opioids: -14.4 [95% CI -25.5, -3.4] centiles), although the results were sensitive to model specifications. Prenatal nicotine and alcohol estimates were in similar directions but not statistically significant. No significant associations between exposures and gestational age at delivery were detected. In this initial HBCD Study data release, more than minimal exposure to cannabis and opioids was associated with smaller birth size, adding evidence to an inconsistent literature. Future studies from HBCD can more deeply interrogate timing and dose of each substance and expand to childhood outcomes.