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Cannabis use during pregnancy: poorer neonatal outcomes

Cate Swannell
Med J Aust
Published online: 15 June 2020

CONTINUING to use cannabis during pregnancy is an independent risk factor for poorer neonatal outcomes, according to the authors of research published by the Medical Journal of Australia today.

A team of researchers from Australia, the UK and New Zealand, analysed data from 5610 pregnant nulliparous women with low risk pregnancies, recruited for the Screening for Pregnancy Endpoints (SCOPE) study, November 2004 – February 2011. At 14–16 weeks of pregnancy, women were grouped by self-reported cannabis use.

They found that 314 women (5.6%) reported using cannabis in the 3 months before pregnancy or during their pregnancy; 97 (31%) stopped using it before and 157 (50%) during the first 15 weeks of pregnancy, while 60 (19%) were still using cannabis at 15 weeks. Compared with babies of mothers who had never used cannabis, infants of those who still used it at 15 weeks had lower mean values for birthweight, head circumference, birth length, and gestational age at birth. The differences for all outcomes except gestational age were greater for women who used cannabis more than once a week than for those who used it less frequently.

“Cannabis is the most frequently used illicit drug in Australia, probably because of its increasing social and medical acceptance, as well as the recent legalisation of cannabis use in many parts of the world,” wrote the researchers, led by Dr Luke Grzeskowiak, from the Robinson Research Institute at the University of Adelaide.

“We found that the frequency of severe neonatal morbidity and death was higher for babies of mothers who continued to use cannabis at 15 weeks, consistent with the results of a recent American study. These findings could reflect the lower gestational age at birth for babies of women who continue using cannabis during pregnancy or be related to altered fetal growth. How cannabis might impair fetal growth or lead to preterm birth is unclear, but we know that components of cannabis can cross the placenta and this raises a number of concerns about effects on child health and development.

“Continued and high frequency of cannabis use during pregnancy were each associated with significantly poorer neonatal outcomes,” Grzeskowiak and colleagues concluded.

“Our findings provide important information for women and health care providers about the potential harms of cannabis use during pregnancy, which is particularly important given the increasing perception in the community that cannabis is a safe drug.”

  • Cate Swannell


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