In a study of 344 Aboriginal women in South Australia, 20.5% used cannabis during pregnancy, and their babies were on average 565 grams lighter with 3.9 times higher odds of low birth weight even after adjusting for social factors.
Pregnant individuals considering cannabis use and healthcare providers working with Indigenous communities.
Babies of cannabis users were 565 grams lighter on average, with 3.9x higher odds of low birth weight
What the researchers found
Researchers surveyed 344 Aboriginal women giving birth in South Australia to assess whether cannabis use during pregnancy was associated with adverse birth outcomes.
One in five women (20.5%) used cannabis during pregnancy, and 52% smoked cigarettes. Compared to mothers who used neither cannabis nor cigarettes, mothers who used cannabis had babies that were on average 565 grams lighter, were 6.5 times more likely to have low birth weight, and 3.8 times more likely to be small for gestational age.
After adjusting for education, social characteristics, and exposure to stressful life events, the odds of low birth weight remained elevated at 3.9 times higher for cannabis-using mothers. The persistence of this association after controlling for social determinants suggests a biological effect of cannabis on fetal growth.
Why it matters
Indigenous communities already experience rates of stillbirth, preterm birth, and low birth weight two to three times higher than other populations. The finding that cannabis use is independently associated with reduced birth weight even after accounting for social factors highlights an additional, potentially modifiable risk factor.
The numbers in context
344 women surveyed. 20.5% used cannabis during pregnancy. 52% smoked cigarettes. Cannabis users' babies were 565g lighter on average. Unadjusted OR for low birth weight: 6.5. Adjusted OR: 3.9. OR for small for gestational age: 3.8.
How the study worked
Cross-sectional, population-based survey of women giving birth to Aboriginal babies in South Australia from July 2011 to June 2013. Data included cannabis use, cigarette smoking, stressful events, social health issues, and birth outcomes (weight and gestational age). Sample of 344 women representative of the broader population.
What this study cannot tell us
Self-reported cannabis use may undercount actual use. The cross-sectional design limits causal inference. Cannabis and cigarette use overlapped substantially, making it difficult to fully separate their effects. The sample represented one geographic region and may not generalize to all Aboriginal communities.
How to read the evidence
This is a population-based cross-sectional study with statistical adjustment for multiple confounders, providing moderate-quality evidence on the association between cannabis and birth outcomes.
When this study was published
Published in 2016. Research on cannabis and birth outcomes has continued, with most studies supporting an association with reduced fetal growth.
The bigger picture
This study adds to the evidence on cannabis and birth outcomes while highlighting the complex interplay between substance use, social determinants, and health disparities in Indigenous communities. The researchers emphasized the need for integrated responses developed collaboratively with Aboriginal communities.
Questions still open
- What mechanisms drive the association between cannabis use and reduced fetal growth? Would culturally appropriate prenatal programs reduce cannabis use and improve birth outcomes in Aboriginal communities?
Common questions
Does cannabis use during pregnancy cause low birth weight?
Is it safe to use cannabis during pregnancy?
Read the original research
Use of cannabis during pregnancy and birth outcomes in an Aboriginal birth cohort: a cross-sectional, population-based study.
BMJ open, 6(2), e010286
Citation
Brown, Stephanie J; Mensah, Fiona K; Ah Kit, Jackie; Stuart-Butler, Deanna; Glover, Karen; Leane, Cathy; Weetra, Donna; Gartland, Deirdre; Newbury, Jonathan; Yelland, Jane. (2016). Use of cannabis during pregnancy and birth outcomes in an Aboriginal birth cohort: a cross-sectional, population-based study.. BMJ open, 6(2), e010286. https://doi.org/10.1136/bmjopen-2015-010286
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