As more states legalize marijuana, more women are talking to their doctors about pot use during pregnancy — and obstetricians are grappling with the best way to have that conversation.

“Women are much more forthcoming about reporting. But we’ve changed the way that we ask as well,” said Dr. Camille Hoffman-Shuler, an OB-GYN at the University of Colorado Anschutz Medical Campus who has studied marijuana use in pregnancy.

Obstetricians say it’s critical that providers start asking women explicitly about marijuana use in pregnancy, because many women don’t consider marijuana a drug and won’t disclose using it when a provider asks broadly about drug use or smoking.

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“It’s important to ask, just like we ask whether you drink alcohol, ‘Do you smoke marijuana or use a CBD cream?’ It’s important to ask specifically,” said Dr. Leena Nathan, an OB-GYN at UCLA Health.

That question, providers say, has grown all the more pressing as pot use seems to be growing more common among pregnant women. A study published earlier this year found that 12% of pregnant women in the U.S. reported using marijuana during the first trimester in 2016 and 2017 — up from just under 6% in 2002 and 2003. Just over 3% of pregnant women reported using marijuana daily or nearly every day. Women with morning sickness and nausea due to pregnancy are more likely to use marijuana, but women also report using it for anxiety, depression, and other health conditions.

That shift has occurred as a growing number of states legalize marijuana for recreational and medical use, making it easier to obtain and stripping away some of the stigma around using the drug. As public perceptions of marijuana change, clinicians say it has become easier to talk to their pregnant patients about using the drug.

“Legalization has helped us have a more open discussion,” Nathan said. “Before, patients wouldn’t even want to discuss it with me or bring it up.”

Professional groups and public health officials largely recommend pregnant and breastfeeding women steer clear of marijuana. Some studies suggest the drug — which can cross the placenta and reach the fetus — is associated with low birthweight and other potential health harms.

Those risks mean many providers are keen to talk about marijuana use during pregnancy — but those conversations don’t always happen. Some patients don’t want to disclose marijuana use out of concern that a health care provider will be required to report them to child protective services officials. Others don’t think to divulge marijuana use during pregnancy, particularly if their providers don’t ask specifically about it.

And even when providers do talk to pregnant women about pot use, providers are sorely lacking information to share. There simply isn’t enough research on the effect of pot on pregnant women or fetuses — nor is there robust evidence on how the risk differs from one strain of marijuana to the next, or among various methods for using the drug.

“It’s a tough issue. There is not evidence that marijuana is safe in pregnancy. There is evidence that there are risks, with low birth weight in particular,” said Marian Jarlenski, a University of Pittsburgh researcher who has studied how women perceive the risk of marijuana use during pregnancy and how obstetricians discuss the subject with patients.

But on the other hand, she said, “we don’t want to be punitive and scaring women and overstating the risks.”

Providers and public health officials are striving to communicate their concerns clearly with people who are pregnant — even as some dispensaries market their products as a way to curb morning sickness or nausea.

“There is this unfortunate public perception that marijuana is safe, when truly what we have is a lack of data. And a lack of data doesn’t mean something is safe — it means there is a lack of data,” said Dr. Albert Hsu, a fertility specialist at MU Health Care in Missouri.

“However, the emerging data is disquieting,” he added.

A study published in July found that women who used marijuana during pregnancy were significantly more likely to deliver before 37 weeks gestation than women who didn’t use the drug. Experts have also expressed concern that, because THC, the ingredient that gives marijuana its high, can cross the placenta, the compound could be adversely affecting fetal brain development.

“We tell pregnant women to stop eating lunchmeat when they’re pregnant unless it’s cooked. Telling them to hold off with cannabis until they’re done being pregnant and breastfeeding, I think it’s appropriate,” Jarlenski said.

If there’s little known about the potential risks of marijuana during pregnancy, there’s far more that isn’t known about the effect of the drug during pregnancy. Experts don’t know if specific strains are associated with certain risks. They aren’t clear on whether THC is to blame for potential problems in pregnancy or whether another component of marijuana is to blame.

And unlike most prescription drugs, the dose of THC in a given amount of marijuana can vary wildly from strain to strain or even plant to plant. That means women — and their doctors — don’t always know how much of the drug they or their fetuses are being exposed to. Researchers are currently running studies to answer some of those questions by asking women who already use marijuana during pregnancy to bring in samples of the products they use. The goal: Look for patterns in health outcomes for women and babies based on the kinds of marijuana they use and how they consume it.

For now, though, the lack of information can make conversations about marijuana somewhat difficult for health care providers to navigate. But it’s not a problem obstetricians are unfamiliar with — many prescription and over-the-counter drugs haven’t been studied for safety or efficacy specifically in pregnant women.

“I have the ‘We-don’t-have-enough-information’ conversation all the time,” said Hoffman-Shuler, the Colorado OB-GYN.

Whether they’re talking about a CBD cream or a prescription nausea pill, Hoffman-Shuler said prenatal providers have to talk with patients about why they want to use a drug, what alternatives exist, and how to balance the potential risks and benefits to both a patient and a fetus.

Hoffman-Shuler noted that because many medications — and in particular, combinations of common drugs used in pregnancy — haven’t been studied well, physicians don’t necessarily know which option is the least risky.

“If I have a woman who has hyperemesis [a pregnancy complication that can cause severe vomiting] and she’s on four different nausea medications, I can’t say that combination is better or worse than if one single agent like marijuana works for you,” she said.

In some cases, providers seem to sidestep the question of marijuana use in pregnancy altogether. In one 2017 study, researchers recorded nearly 500 first appointments between a pregnant patient and obstetric provider, in which nearly 20% of patients reported marijuana use. But in nearly half of the conversations with women who said they were using pot, obstetric providers didn’t say anything or offer the patient any kind of counseling about marijuana use in pregnancy.

When they did offer feedback, providers largely offered generalized statements, mentioned toxicology testing, or warned women that a positive THC test at delivery might mean child protective services would become involved. They focused far less on the health implications.

“What providers should be saying [is] quickly evolving as we start to see more studies come out,” said Jarlenski.