# Association Between Prenatal Cannabis Exposure and Child Health Care Use: A Retrospective Cohort Study in Ontario, Canada

## TL;DR

Children exposed to cannabis in the womb had fewer primary care visits but more specialist visits compared to unexposed children.

## Contribution

This study identifies long-term health care use patterns linked to prenatal cannabis exposure using a large population-based cohort.

## Key findings

- Prenatal cannabis exposure was associated with fewer primary care visits (aRR: 0.86).
- It was linked to increased outpatient psychiatrist visits (aRR: 1.29), emergency department visits (aRR: 1.05), and hospitalizations (aRR: 1.12).
- Among high-income groups, cannabis use doubled the rate of outpatient psychiatrist visits.

## Abstract

Cannabis use among expectant mothers has increased steadily over the past two decades. We compared the long-term health services use of offspring prenatally exposed to cannabis to that of matched, unexposed offspring.

We conducted a retrospective cohort study using linked perinatal and health administrative databases of all live, singleton births in Ontario, Canada hospitals between April 1, 2007 and March 31, 2012. Infants were followed until March 31, 2017, with a primary outcome of primary care visits up to age 10. Secondary outcomes included rates of outpatient psychiatrist visits, emergency department visits and hospitalizations. We used adjusted Poisson regression to assess differences in rates of health service use between children with and without exposure to prenatal cannabis.

We included 508 025 infants, 3248 (0.6%) had cannabis exposure. Prenatal cannabis use was associated with a decreased rate of primary care physician visits (adjusted rate ratio [aRR]: 0.86, 95% confidence interval [CI]: 0.84-0.87) and an increase in the rate of outpatient psychiatrist visits (aRR: 1.29, 95% CI: 1.00-1.66), emergency department visits (aRR: 1.05, 95% CI: 1.03-1.08), and hospitalizations (aRR: 1.12, 95% CI: 1.04-1.20). Among preterm offspring, cannabis was associated with a decrease in primary care visits but no difference in other visits. Among those in the highest income quintiles, cannabis use was associated with a two-fold increase in the rate of outpatient psychiatrist visits.

Offspring exposed to prenatal cannabis receive fewer primary care visits but have increased rates of visiting health care specialists past the neonatal period.