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A new study has found that babies exposed to cannabis in the womb may be at greater risk of certain adverse birth outcomes such as low birth weight and preterm birth.
A peer-reviewed study published Thursday in Addiction was a meta-analysis, or a compilation of information from 57 previous studies. Data samples from just under 13 million infants were analyzed including 102,835 infants who were prenatally exposed to cannabis. Data surrounding the frequency of preterm birth, low birth weight and NICU admissions collectively ranged from 1.5 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.
- 20 of the studies analyzed looked at possible associations between cannabis use and preterm birth. Infants exposed to intrauterine cannabis in these cases were reportedly over 1.5 times as likely to deliver early compared to infants who were not.
- 18 of the studies analyzed possible associations between low birth weight and intrauterine cannabis exposure. Infants exposed to cannabis in these cases were over twice as likely to be born at a low weight than infants who were not exposed.
- Ten of these studies looked at possible associations between rates of NICU admissions in infants and found that infants who were exposed to cannabis were over twice as likely to be admitted to intensive care than those who were not exposed.
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.”