Doctors worried about increased marijuana use in pregnant women Fourteen percent of pregnant women ages 12-17 admitted using marijuana.

 -- As more states legalize recreational marijuana -- and its use continues to climb -- the number of pregnant women using the drug has doctors concerned.

The American College of Obstetrics and Gynecology (ACOG) recommends pregnant women avoid marijuana due to evidence that it affects the fetus and that it may interfere with brain development.

Yet young pregnant women report using the drug at an alarming rate, according to a study published in the Annals of Internal Medicine earlier this month. A whopping 14 percent of pregnant women aged 12 to 17 reported using the drug in the past month, compared to just 6 percent of their non-pregnant peers, according to data from 410,000 women between the ages of 12 and 44 collected by the National Survey on Drug Use and Health between 2002 and 2015.

“Those numbers are very distressing,” said Nora Volkow, an author of the study and director of the National Institute on Drug Abuse. “Teenagers who get pregnant are the ones at greatest risk of having poor [pregnancy] outcomes, and then on top of that, you have the effect of teenage women smoking marijuana while they are pregnant.”

Risk-taking behavior among young women may be one reason for this high rate

“Sex, drugs, and rock and roll go together for a reason,” said Stuart Gitlow, an addiction psychiatrist and past president of the American Society of Addiction Medicine. “People do them as a method for rebelling outside the parameters of what they are supposed to do.”

But experts believe a growing acceptance of marijuana -- recreational and medicinal -- also plays a significant role in the drug's popularity. Between 2001 and 2013, marijuana use rates in the United States more than doubled. And the rates of pregnant women using the drug jumped from 2.4 percent to 3.9 percent in 2001 and 2014, respectively, according to research published in the Journal of the American Medical Association earlier this year.

Because some people use marijuana for nausea, women who are pregnant may think the drug is a “natural” way to combat morning sickness, Gitlow said.

“That is unfortunate because it implies that it is safe,” he said. "Yet nothing could be farther from the truth.”

Doctors who care for pregnant women should screen for marijuana use and advise these patients against it, the ACOG recommends. Physicians say women are usually receptive to this advice.

“Being pregnant often has a really strong influence on a woman’s life,” said Roshini Zachariah, a resident physician in obstetrics and gynecology at the University of Washington. “They may think, I want to do everything right for my baby.”

Explaining the risks marijuana poses during pregnancy is usually enough to convince women to stop using it. But if all else fails, mentioning that a doctor must notify child protective services if a pregnant woman is using drugs often is a wake-up call.

“They run the risk of losing their baby,” Gitlow said.

Of course, it’s a big challenge to convey the message to women who don’t have contact with the health care system, so public health campaigns should focus on dispelling the myth that weed is safe during pregnancy.

“It highlights the importance of educating the public on measures that could protect the newborn,” said Volkow.

Allison Bond, MD, is a resident in internal medicine at Massachusetts General Hospital and a former medical resident at the ABC News Medical Unit. Follow her on Twitter @AllisonRBond.