5 to over two times as likely in the infants exposed to cannabis than in those who were not.  “Prenatal cannabis use appears to be associated with lower birth weight, preterm birth and neonatal intensive care unit admission in newborns, but there is little evidence that prenatal cannabis exposure adversely impacts behavioral or cognitive outcomes in early childhood, with the exception of attention and externalizing problems,” the study said.  According to the study, cannabis use during pregnancy did not lead to higher rates of infant mortality, Sudden Infant Death Syndrome or birth defects.

However, of the 57 studies analyzed, at least 48 of them registered higher rates of low birth weight, preterm birth and NICU admissions. First author of the study and PhD Candidate at the Institute of Medical Sciences, University of Toronto Ms. Maryam Sorkhou said in a written statement that this study reinforces data showing THC can enter the placenta when used during pregnancy. “The global increase in cannabis use among women of reproductive age also extends to pregnant women. We know that THC, the main psychoactive constituent in cannabis, can cross the placenta from mother to fetus and bind to receptors in the fetal brain,” said.

“Our study adds to that knowledge by showing that prenatal exposure to cannabis heightens the risk of several adverse birth outcomes.” There are many drawbacks to this study and how the data was presented that should be taken into consideration before drawing any drastic conclusions, primarily sample size. The sample size of infants who were not exposed to cannabis compared to those who were was 130:1 in this case. Additionally, the study offered no data on exposure to other drugs during pregnancy, a litany of which are known to cause adverse birth outcomes similar to those named in this study.

Cannabis use does not necessarily indicate the use of other drugs, but that data would have been a welcome addition to the rest of the data presented from this study.  The topic of cannabis use during pregnancy is still a bit of a mixed bag. A 2019 study found that cannabis use during pregnancy is increasing in the United States. There have also been previous studies that found negative correlations between cannabis use and pregnancy, including another meta-analysis in 2022 that looked at 27 previous studies from between 1986 and 2022 and found cannabis use carried an increased risk for preterm births.

However, another study published just this year that looked at data from just under 3,000 births that took place between 1989 and 1993 and found that cannabis use during pregnancy did not increase the child’s risk for mental impairments or cognitive disorders. A NORML review of this study in 2017 said the following: [The] evidence base for maternal-infant health outcomes of cannabis use in pregnancy is more robust than for many other substances. … Although there is a theoretical potential for cannabis to interfere with neurodevelopment, human data drawn from four prospective cohorts have not identified any long-term or long-lasting meaningful differences between children exposed in utero to cannabis and those not.

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