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Californian Women Are Increasingly Using Cannabis While Pregnant, Study Finds

By Leo Bear-McGuinness

Published: Jul 19, 2019   
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More West-coast women are “toking for two” and putting their unborn children at risk, according to an observational study of pregnant women in northern California.

After studying the questionnaire results from nearly 277,000 women, researchers reported that marijuana use in the year prior to pregnancy had increased from 6.8 percent in 2009 to 12.5 percent in 2017, while cannabis use during pregnancy jumped from 1.95 to 3.38 percent in the same timeframe. 

The effects of cannabis consumption on a developing fetus are still largely unknown, but recent studies have linked the habit to higher likelihoods of preterm births and of unborn children developing psychosis later in life. 

Due to these known risks, doctors at Kaiser Permanente, the multi-state healthcare corporation that led the new northern Californian study, encourage pregnant patients to halt their cannabis use, and regularly screen pregnant women for the drug as a standard self-report. A previous study from the organization found that the number of these marijuana-positive reports nearly doubled between 2009 and 2016, from 4 percent to 7 percent. 

The latest research from the healthcare company, published in JAMA Network Open, was the first of its kind to assess prenatal marijuana use in pregnant women. 

Marijuana and pregnancy

“We wanted to know whether trends were changing over time and how frequently women were saying that they use cannabis during pregnancy,” said Kelly Young-Wolff, a research scientist at the Kaiser Permanente Northern California Division of Research and lead author of the study.

“So, one of the main findings is that by 2017, among those women who said ‘yes, I've used cannabis during pregnancy,’ 21 percent of them said that they were using cannabis daily,” she told Analytical Cannabis.”

From 2009 to 2017, the study found that daily use of marijuana in the year prior to pregnancy increased from 1.17 percent to 3.05 percent, while daily use during pregnancy more than doubled from 0.28 to 0.69 percent.

“Ninety-six percent of our women who said they used during pregnancy were also using in the year before pregnancy," said Young-Wolff. "And I think that is actually a nice thing to know, because women's health clinicians can provide education about the potential harms of prenatal cannabis to all women of reproductive age, particularly those who are trying to get pregnant prior to conception.”

Limitations and future research

But while the study’s findings may become valuable to health professionals, its data were sourced prior 2018 – the year recreational cannabis became legal in California – an omission that may make it difficult to judge how accurately the study’s figures represent current, legal consumption rates among pregnant women in the state. 

“We think it's going to be important to continue to monitor whether prenatal cannabis use increases even further now that California has legalized recreational use,” Young-Wolff added.

“So, we'll be looking at whether prenatal cannabis use is associated with increased risk of maternal, fetal, and neonatal outcomes using our data set. And then we'll test whether the legalization of cannabis for recreational use in California in 2018 is associated with greater increases in use.” 

Other future research efforts may endeavour to expand the scope of Kaiser Permanente's survey, to help differentiate between the different types of cannabis products pregnant women use and the different prenatal effects they may have. 

“We just looked at any self-reported cannabis use,” Young-Wolff said. “And so we think that additional studies are definitely needed to look at alternative forms of consumption. How are women using? Are they vaping? Are they using edibles? And then also to look at the potential variations and health effects of those different modes of administration.”

Considering the varied legalization landscape of the US, Young-Wolff also notes that the study’s conclusions may not be generalizable to women outside of California or those without access to health care. However, the general conclusions are in agreement with a separate, nationally representative study from earlier this year, which found that the adjusted prevalence of past 30-day cannabis use in pregnant women aged 18 to 44 years rose from 2.37 percent in 2002 to 3.85 percent in 2014.

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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