Pregnant women who use marijuana have babies with lower birth weights: a study

A low birth weight creates an increased risk of diabetes, heart disease, and even obesity.

May 3, 2018
Pregnant Women Who Use Marijuana Have Babies With Lower Birth Weights: A Study

a smoking and drinking pregnant immigrant woman lying in bed, expecting a baby boy in the coming days. ( Photo by dblight via Getty Images )

As marijuana legalization spreads, many are concerned about the unintended consequences on public health. One major concern is a potential increase of marijuana use among pregnant mothers. Already, some studies have found a slow increase in prenatal marijuana use over the past few decades.

Now, a new study from the Colorado School of Public Health, published in The Journal of Pediatrics, found that marijuana use could result in a lower birth weight among newborns. Among the study’s participants, marijuana use during pregnancy increased this likelihood by 50 percent. The results persisted regardless of tobacco use or the age of the mother.

The study was conducted using data from 3,207 women, who had responded to the 2014-2015 Colorado Pregnancy Risk Assessment Monitoring System. This monitoring system operates by surveying women via mail or by phone who have recently given birth. 

According to the study, 5.7 percent of mothers surveyed in Colorado used marijuana while pregnant, and five percent used marijuana while breastfeeding. The complications associated with low birth weight include an increased risk for diabetes, heart disease, and even obesity.

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NICU baby is nurtured by mother (Photo by Jill Lehmann Photography via Getty Images)

The study found that a mother’s age, education and economic circumstances also predicted her likelihood of marijuana use while pregnant. Respondents who were young mothers—white, poor, less educated, unmarried, and enrolled in Medicaid or WIC—used marijuana during pregnancy at a rate three to four times higher than other respondents.

“Our findings underscore the importance of screening for cannabis use during prenatal care and the need for provider counseling about the adverse health consequences of continued use during pregnancy and lactation,” concludes the study.

Other studies, like one published in Australia in 2012, have similarly found an association between marijuana use during pregnancy and lower birth weights.

“There is increased availability, increased potency and a vocal pro-cannabis advocacy movement that may be creating a perception that marijuana is safe to use during pregnancy,” wrote Tessa L. Crume, the study’s lead author. According to Colorado’s Department of Public Health and Environment, the state has one of the most significant low birth weight rates in the nation.

However, findings from other studies refute evidence that prenatal marijuana use has negative outcomes. One study in Jamaica, for example, found that 30-day-old babies of mothers who had consumed marijuana while pregnant actually scored better on reflex and autonomic stability tests.

Some mothers who advocate for marijuana use during pregnancy have cited this conflicting evidence and the fact that birth complications can arise from other prescription medications. However, health professionals insist that not enough research exists to support either conclusion. Therefore, most health professionals agree that pregnant mothers are best erring on the side of caution and abstaining from prenatal marijuana use for now.

May 3, 2018