An increasing number of women are using cannabis before becoming pregnant, as well as early in the pregnancy, according to a new study published Friday in the journal JAMA Network Open.
The findings, from Kaiser Permanente Northern California, are based on reports from 276,991 women living in California before recreational marijuana was legalized in that state. The women were asked about their cannabis use at their first prenatal visit, NBC News reports.
The data showed that prevalence of women who reported using marijuana during the year before pregnancy grew from 6.8% in 2009 to 12.5 percent in 2017. The number of women who said they used marijuana while pregnant was much smaller; however, that prevalence also increased from 1.9% in 2009 to 3.4% in 2017.
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But there's no evidence that cannabis is safe for pregnant women.
"No amount of cannabis use has been shown to be safe during pregnancy," said Kelly Young-Wolff, lead author of the new report and a research scientist with Kaiser Permanente Northern California. "We do know that cannabis crosses the placenta and reaches the fetus."