Pregnant Women Using Cannabis Numbers 'Rapidly Increasing,' Experts Warn

Cannabis use among pregnant women is "rapidly increasing," according to researchers who studied hundreds of thousands of expectant mothers.

More women are using cannabis every day in the run-up to and during their pregnancy, a paper published in the journal JAMA Network Open found. However, the data was collected during the women's initial prenatal visit. This usually takes place at around 8 weeks of pregnancy, when women may not yet realize they are pregnant.

As cannabis has been legalized in several states over recent few years, the drug has become more acceptable and accessible, the authors wrote. Existing studies show more women are using weed during pregnancy, and the researchers wanted to learn more about the frequency.

The researchers warned using cannabis during pregnancy could harm both the mother and the developing fetus, causing low birth weight and poor neuropsychological functioning in children.

The new study involved 276,991 women, representing 367,403 pregnancies, who completed a questionnaire about marijuana use while they were having prenatal care at Kaiser Permanente Northern California. In the surveys filled out between January 1, 2009, and December 31, 2017, the women wrote how often they used cannabis before and during pregnancy. Most of the women involved were white, followed by Hispanic, Asian, and African American.

The number of women who said they took the drug daily, weekly, or monthly rose significantly, the team said, with daily use rising fastest.

By 2017, the authors found women consuming cannabis a year before their pregnancy rose from 6.8 percent to 12.5 percent.

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A stock image of a woman rolling a joint. Research suggests the number of women using cannabis in the lead up to their pregnancy is rising. Getty

Of the women who used cannabis the year before they became pregnant, 17 percent said they used it daily. That rose to a quarter by 2017. Weekly users climbed from 20 percent to 22 percent. But monthly-or-less users dropped from 63 percent to 53 percent.

Expectant mothers who used cannabis during pregnancy daily rose from 15 to 21 percent. The corresponding move was 25 percent to 27 percent in the weekly group, but once again fell from 60 percent to 52 percent in the monthly-or-less group.

Study co-author Kelly C. Young-Wolff, a research scientist at Kaiser Permanente Northern California, told Newsweek: "The goal of our research is to help empower women to make informed decisions to protect their health and the health of their baby.

"Prenatal substance use is a highly sensitive topic and it is an important challenge for our team to ensure that data from our research not be used to exploit or stigmatize women."

She continued: "We believe that women deserve non-punitive healthcare where they feel free to disclose substance use and get help when needed. We have demonstrated that our Early Start Program in Kaiser Permanente, which links a substance use intervention with prenatal care, helps pregnant women to stop substance use in pregnancy, and is associated with improved prenatal outcomes and reduced healthcare costs."

Associate Professor Miranda Reed at Auburn University, Harrison School of Pharmacy, who did not work on the research, told Newsweek: "This study is significant because it shows cannabis use among women during pregnancy is rapidly increasing."

She said: "Most surprising is the extent by which cannabis use during pregnancy increased despite existing and new evidence suggesting the adverse effects on the fetus."

Professor Vishnu Suppiramaniam of the Administration of Auburn University, Harrison School of Pharmacy, told Newsweek: "This study might indicate that legalization of cannabis use may increase use during pregnancy or that there is an increased belief that use during pregnancy is safe."

More research is needed to uncover the potential harm of perinatal cannabis use, the authors said. Separate studies due to be published in the autumn by Suppiramaniam and Reed indicate that using cannabis during pregnancy leads to long-term effects on learning and memory mainly due to modification of specific neurotransmitter systems.

Earlier this year, a separate team of researchers published a study warning women using cannabis while pregnant to ease morning sickness could damage the brain of a fetus. The researchers arrived at their conclusion after studying rats.

The work was presented at the American Society for Pharmacology and Experimental Therapeutics annual gathering during the 2019 Experimental Biology meeting. The work was therefore not published in a peer-reviewed journal.

Associate Professor Ryan Bogdan of the Department of Psychological and Brain Sciences at Washington University in St. Louis, who didn't work on the paper, told Newsweek the findings of the new study would have been more robust if the authors looked at how and when the women used the drug. He also said relying on the participants to accurately state how much weed they use can present problems, owing to the stigma associated with the substance.

"As women may use cannabis for a host of different reasons, obtaining reported reasons for using may help understand why women are using so that these issues may be addressed," he said.

Bogdan said the problem could be explained by evidence suggesting licensed dispensaries, particularly those licensed for medical marijuana, have been known to recommend marijuana as a treatment for pregnancy-related nausea.

Warning of the potential harms, he said: "The main psychoactive component of marijuana, tetrahydrocannabinol, can cross the placental barrier to gain access to the developing fetus.

"We know remarkably little about the potential consequences of cannabis exposure, particularly during the prenatal period. This is particularly alarming as non-human animal studies have shown that the neurochemical system that marijuana interacts with, the endocannabinoid system, plays an important role in neurodevelopment.

"As such, it is possible that marijuana exposure may have unique effects at different developmental periods. Human studies have inconsistently linked prenatal marijuana exposure to reduced birth weight, reduced cognitive performance, and increased risk for psychopathology including liability to schizophrenia."

It's not clear if these issues happen because of prenatal marijuana use, or if women who use marijuana during pregnancy also happen to have a higher genetic liability for schizophrenia, he said.

"Nonetheless, given the possibility that marijuana use during pregnancy may impact neurodevelopment and confer increased risk for a host of negative outcomes among children, its use should be discouraged during pregnancy," said Bogdan.

This piece has been updated to clarify that Miranda Reed was not involved in the research, and include comment from Kelly C. Young-Wolff.