A study of almost 5 million live births in California by researchers at the Herbert Wertheim School of Public Health and Human Longevity Science at University of California San Diego reports that babies born to mothers diagnosed with cannabis use disorder were more likely to experience negative health outcomes, such as preterm birth and low birth weight, than babies born to mothers without a cannabis use disorder diagnosis.

The findings are published online in the April 22, 2021 issue of the journal Addiction. The National Institute on Drug Abuse, part of the National Institutes of Health, funded the study.

Cannabis use disorder is a diagnostic term with specific criteria that defines continued cannabis use despite consequent, clinically significant impairments. The research team, led by first author Yuyan Shi, PhD, associate professor at The Herbert Wertheim School of Public Health, conducted a retrospective cohort study of 4.83 million mothers who delivered live, single births in California from 2001 to 2012.

They identified 20,237 women who were discharged after delivery with a diagnosis of cannabis use disorder. Not all people who use cannabis meet the criteria for cannabis use disorder. The study authors stated the actual incidence of cannabis use disorder is likely higher than reported numbers.

The researchers found that diagnoses of cannabis use disorder, based on medical records at time of delivery, rose from 2.8 to 6.9 per 1000 deliveries from 2002 to 2012. Compared to a matched control group of 40,474 mother-infant pairs, infants born to women with cannabis use disorder were more likely to be born preterm, have a low birth weight and be small for their gestational age, all factors that can require greater or more intense medical care or presage later health issues.

Additionally, researchers found that, though rare overall (less than 1%), the risk of infant mortality was greater for infants born to women with cannabis use disorder. These infants were 35% more likely to die within a year of birth than infants in the control group. Conversely, these infants were also less likely to be hospitalized within the first year of life than control group infants.