Tags:  Pregnancy; cannabis use; birth outcomes

 

The problem: Cannabis use often correlates with other substance use (e.g. tobacco, alcohol), and studies that characterize the impact of maternal cannabis use on birth outcomes are often confounded by these factors. Hence, the unique contribution of in utero cannabis exposure on birth outcomes have not been fully characterized.

 

The study:  The objective of this study was to examine the association between biochemically confirmed cannabis exposure late in pregnancy and birth outcomes, using data from two independent cohorts (Appalachian and Rocky Mountain).

 

Main results: In the Appalachian cohort, participants were identified by a retrospective review of 18,728 births over a five-year period; in the Rocky Mountain cohort, they were identified via a prospective review of 12,443 births over a four-year period. Participants with cannabis exposure were identified using a urine drug screen at delivery. Cannabis-exposed participants were matched to an equal number of unexposed participants who had no cannabis exposure during pregnancy/delivery. Other criteria, such as tobacco, alcohol or other drug use during pregnancy were monitored by either self-reporting or urine drug screens during pregnancy/at delivery. Together, the study included 1062 mother–newborn dyads (cannabis-exposed: n= 531; cannabis-unexposed: n=531).

 

• Newborns exposed to cannabis in utero had significantly lower Apgar scores (1 min and 5 min) and had a lower birth weight (218 g less), compared to those unexposed to cannabis.

• Compared to newborns unexposed to cannabis, those exposed to cannabis in utero were:

  • 82% more likely to have a low birth weight (under 2.5 kg)

  • 79% more likely to be born preterm (less than 37 weeks of gestation)

  • 43% more likely to be admitted to the neonatal intensive care unit (NICU) following delivery

Conclusions:  Infants who were exposed to cannabis in utero had significantly worse birth outcomes, compared to those who were unexposed to cannabis.

 

Why this is a good study:

• This study included data from two large population-based cohorts in the United States, and hence, the findings may be broadly applicable.

• The authors utilized biochemical determination of cannabis (and other drug) exposure. This allowed for a clear classification of participants into the cannabis-exposed or unexposed groups.

• Rigorous matching was also performed between participants in the cannabis exposed and unexposed groups, adding strength to the analysis.

 

Why this isn’t a perfect study:

• Cannabis exposure was based on a positive urine drug screen at delivery, which typically indicates use within the last 48–72 hours. Thus, if participants had used cannabis outside this window, they would not be included in the cannabis-exposed group.

 

What this study adds:

• The study findings add to the growing body of research linking in utero cannabis exposure to adverse birth outcomes.

 

What it doesn’t:

• The amount of cannabis consumed was not recorded in this study; therefore, the amount that is necessary to bring about the adverse health outcomes were not recorded.

• Further, the impact of cannabis (and other drug) exposure earlier in the pregnancy was not measured, as the drug screens were performed only at the time of delivery.

 

Funder: The Tennessee portion was funded by Johnson City Junior League, Departments of Pediatrics and Family Medicine, and the Center for Prescription Drug Abuse and Misuse, at East Tennessee State University. The Colorado portion was funded by the Department of Obstetrics and Gynecology, University of Colorado.

 

Author conflicts:  None