With Americans becoming more accepting of smoking marijuana, one report warns against those changing attitudes extending to drug use among pregnant women.

According to a letter in the Journal of the American Medical Association, almost 4 percent of expectant mothers reported using marijuana in the previous month in 2014 — up from about 2.4 percent in 2002. And it’s possible the number has continued to rise in the time since, as states have been legalizing medical and recreational use of the drug in recent years. “Between 2001 and 2013, marijuana use among U.S. adults more than doubled … and attitudes toward marijuana became more permissive.”

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About half of the country has legalized medical marijuana and several more are thinking about following suit. But a more positive public opinion of weed doesn’t make it any more healthy for a developing baby. The University of California, Los Angeles, said in a statement about the federal report that marijuana may be appealing to these women because it offers relief from the anxiety, pain and nausea that comes with pregnancy. However, while some research says otherwise, marijuana has been linked to a decreased IQ and difficulty concentrating for the baby, as well as a low birth weight.

The Mayo Clinic takes its own warning a step further, advising women against smoking weed while they are breastfeeding as well, as the substance may get into breastmilk and pass to the baby. It cites side effects for the child like cancer and “development problems.”

“The prevailing science is that marijuana is detrimental to the fetus,” UCLA obstetrician-gynecologist Dr. Leena Nathan said in the university’s statement. “Consuming edible marijuana is sometimes perceived as safer than smoking it, but I advise pregnant women against both. You may, in fact, experience more THC exposure when eating marijuana rather than smoking it, so there could potentially be an even greater health risk to the fetus.”

To manage anxiety, morning sickness and pain, Nathan recommended exercise and approved medications instead of marijuana. Additionally, over-the-counter treatments like vitamin B6, ginger and acetaminophen could help.

“The American College of Obstetricians and Gynecologists recommends that pregnant women and women contemplating pregnancy be screened for and discouraged from using marijuana and other substances,” the report in the Journal of the American Medical Association said.

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