Background
The full spectrum of associations between in utero cannabis exposure and adverse neonatal outcomes is still unclear.
Objective
This study aimed to evaluate the associations between in utero cannabis exposure and neonatal outcomes.
Study Design
This population-based retrospective cohort study of singleton births among Kaiser Permanente Northern California members (January 1, 2011–July 31, 2020) included parent–infant dyads in which the pregnant parent was screened for cannabis use as part of standard prenatal care, generally upon entrance into care. Data were ascertained from electronic health records. Generalized estimating equation models were adjusted for sociodemographic characteristics, other non-cannabis prenatal substance use, medical and mental health comorbidities, and adequacy of prenatal care. In utero cannabis exposure was defined as self-reported use since becoming pregnant and/or a positive urine toxicology test for cannabis at any time during pregnancy (yes/no; primary exposure). Frequency of use was self-reported and categorized as daily, weekly, monthly or less, never, or unknown (secondary exposure). Neonatal outcomes included low birthweight, small for gestational age, preterm birth, neonatal intensive care unit admission, and infant respiratory support.
Results
Of 364,924 infants, 22,624 (6.2%) were exposed to cannabis in utero. After adjustment for potential confounders, including in utero exposure to other substances, in utero exposure to cannabis was associated with greater odds of low birthweight (adjusted odds ratio, 1.20; 95% confidence interval, 1.12–1.28), small for gestational age (adjusted odds ratio, 1.24; 95% confidence interval, 1.18–1.30), preterm birth (<37 weeks; adjusted odds ratio, 1.06; 95% confidence interval, 1.00–1.13), and neonatal intensive care unit admission (adjusted odds ratio, 1.06; 95% confidence interval, 1.01–1.11). There was a suggestive association with early preterm birth (<34 weeks; adjusted odds ratio, 1.11; 95% confidence interval, 1.00–1.23; P=.055), but no significant association with respiratory support (adjusted odds ratio, 1.07; 95% confidence interval, 0.97–1.18). Dose–response analysis found an increasing likelihood of low birthweight and small for gestational age with increasing frequency of prenatal cannabis use by the pregnant individual. Sensitivity analyses further supported an increased likelihood of low birthweight and small for gestational age, although associations with other outcomes did not reach statistical significance.
Conclusion
In utero cannabis exposure was associated with increased likelihood of low birthweight, small for gestational age, preterm birth, and neonatal intensive care unit admission. Clinicians should counsel individuals who are pregnant or considering pregnancy about the potential adverse neonatal health outcomes associated with prenatal cannabis use.