Women who used marijuana during pregnancy were at increased risk for adverse neonatal outcomes, based on data from a meta-analysis of nearly 60,000 individuals.
Marijuana misuse remains a top substance use disorder and studies of prenatal use show a prevalence as high as 22% worldwide, wrote Greg J. Marchand, MD, of the Marchand Institute for Minimally Invasive Surgery, Mesa, Ariz., and colleagues.
Dr. Greg J. Marchand
“The prevalence of marijuana use during pregnancy may continue to increase, given that there is a suggested association between legalized recreational marijuana and increased use in prenatal and postpartum periods,” they wrote. “Remarkably, 34%-60% of individuals who use marijuana keep using it during pregnancy,” and many women cite a belief that marijuana is safe to use while pregnant, they noted.
Cannabinoid receptors are present in the developing fetus by the start of the second trimester, and exposure to exogenous cannabinoids may be associated with changes in the prefrontal cortex, including development and function, the researchers said. However, previous studies of an association between maternal marijuana use and poor neonatal outcomes have been inconsistent, they added.
In a study published in JAMA Network Open, the researchers identified 16 interventional and observational studies including 59,138 patients; each study included pregnant women who were exposed to marijuana, compared with those not exposed to marijuana, along with neonatal outcomes. The data selection included studies published until Aug. 16, 2021, and 10 studies were published in 2015 or later.
Overall, the risk for seven adverse neonatal outcomes was significantly increased among women who were exposed to marijuana during pregnancy, compared with those not exposed. The researchers identified increased risk for birth weight less than 2,500 g (relative risk, 2.06; P = .005), small for gestational age (RR, 1.61; P < .001), preterm delivery (RR, 1.28; P < .001), and NICU admission (RR, 1.38; P < .001). In addition, they found significant differences in mean birth weight (mean difference, −112.30 g; P < .001), Apgar score at 1 minute (mean difference, −0.26; P = .002), and infant head circumference (mean difference, −0.34cm; P = .02) between women who used marijuana during pregnancy and those who did not.
The study findings were limited by several factors, including the assessment of only cohort studies, which might suffer from bias given their retrospective designs, the researchers noted. Other limitations included the reliance on self-reports, the inability to adjust for tobacco/marijuana coexposure, and the lack of differentiation between levels of use and between different types of marijuana ingestion, they added.
However, the results support an association between marijuana use and adverse neonatal outcomes, and the researchers recommended additional studies of both maternal and neonatal outcomes associated with marijuana exposure. “Given increasing marijuana legalization and use worldwide, raising awareness and educating patients about these adverse outcomes may help to improve neonatal health,” they concluded.
New research prompted new review
The motivation to conduct this analysis at this time was prompted by the publication of several new, high-quality studies on the use of marijuana in pregnancy, according to Dr. Marchand. “It’s been a few years since a full analysis of all of the available data had been done, so we decided it was time to see if the old conclusions still held,” he said in an interview.