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Is Cannabis Safe When Pregnant? Study Seeks Answer, Draws Critics

August 7, 2019
header image: is cannabis safe during pregnancy?
In this Friday, July 26, 2019 photo, Leslie Siu poses for a portrait next to her cannabis products geared toward women on display in Groundswell dispensary in east Denver. Pregnancy started out rough for her. Morning sickness and migraines had her reeling and barely able to function at a demanding New York marketing job, so like rising numbers of U.S. mothers-to-be, she turned to marijuana. “l was finally able to get out from under my work desk,” said Siu, who later started her own cannabis company and says her daughter, now 4, is thriving. (David Zalubowski/AP)
CHICAGO (AP) — Pregnancy started out rough for Leslie Siu. Morning sickness and migraines had her reeling and barely able to function at a demanding New York marketing job, so like rising numbers of U.S. mothers-to-be, she turned to marijuana.


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“l was finally able to get out from under my work desk,” said Siu, who later started her own cannabis company and says her daughter, now 4, is thriving.

There’s no proof that cannabis can relieve morning sickness, and mainstream medicine advises against use in pregnancy because of studies suggesting it might cause premature birth, low birthweight and infant brain deficits. But the National Institute on Drug Abuse is pressing for more solid evidence. Many of those studies were in animals or complicated by marijuana users’ other habits and lifestyles.

“I don’t want us to cry wolf,” said Dr. Nora Volkow, the agency’s director. “We have to do these studies in a way that can identify risks.”

“It's risky to do studies of potentially risky drugs but it's risky not to do studies.”
Dr. John Lantos, Children's Mercy Hospital, Kansas City, MO

With nearly $200,000 from her agency, University of Washington scientists in Seattle are seeking clearer answers in a new study investigating potential effects on infants’ brains. The agency is supporting three similar studies in other states.

In Seattle, they’re enrolling pregnant women during their first trimester who are already using marijuana for morning sickness. Researchers don’t provide the pot, and the use of other drugs, tobacco and alcohol isn’t allowed. Infants will undergo brain scans at 6 months and will be compared with babies whose mothers didn’t use marijuana while pregnant.

For government and university authorities, it’s worthy research that takes advantage of a booming trend. Recent data show the number of pregnant U.S. cannabis users has doubled since 2002, with 7% reporting recent use and higher rates in some states.


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But some opponents of recreational marijuana who think the science is settled have complained to the university and the federal government, calling it bogus research that endorses drug use and needlessly endangers fetuses.

The criticism underscores the challenges of investigating how drugs of any kind affect pregnant women and their offspring.

“There are so many reasons NOT to study drugs — particularly fear of causing birth defects. But the results would be no studies of the drugs’ efficacy during pregnancy, or the risks to the fetus,” said Dr. John Lantos, director of pediatric bioethics at Children’s Mercy hospital in Kansas City, Missouri. “It’s risky to do studies of potentially risky drugs but it’s risky not to do studies.”

Among the most tragic examples is thalidomide, a drug developed in Germany in the 1950s as a sedative. It was later widely promoted and prescribed to treat morning sickness, mostly in western Europe and Canada, despite a lack of research in pregnant women. It soon became linked with severe birth defects and was removed from most markets by the early 1960s.


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The U.S. Food and Drug Administration never approved thalidomide for morning sickness because of safety concerns. The agency has approved a synthetic version of THC, the part of marijuana that causes a high, for AIDS-related appetite loss and a similar drug for nausea caused by cancer drugs, but has not approved it for morning sickness.

Scientist Natalia Kleinhans is leading the University of Washington’s study, aiming to recruit 35 pregnant marijuana users and 35 pregnant women who didn’t consume.

The cannabis consumers are asked to buy from licensed dealers and photograph it so researchers can calculate the THC and CBD, another compound that doesn’t cause a high. Participants are paid $300 but can quit consuming anytime and remain in the study.

Medical and recreational marijuana are legal in Washington state, and Kleinhans says women who use it for morning sickness are different from pregnant pot users in years past, who often did other drugs, smoked or drank.


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“They’re making a choice that people might not agree with. But it’s not out of desperation. It’s an informed choice,” said Kleinhans, a brain imaging specialist who studies the brain and behavior.

Study opponents contend that researchers are recruiting marijuana addicts, that payment encourages participants to keep using, that women aren’t being adequately informed of risks, and that babies will be harmed by being tested. Researchers say MRI brain scans are safe and that infants will be tested while sleeping so won’t need potentially risky sedatives.

While more than 30 states have legalized marijuana for medical and/or recreational use, opponents also note that the federal government still considers pot an illegal drug — a stance that scientists say has hampered research.

“We shouldn't assume that because we classify something as illegal that it is shameful.”
Dr. Mishka Terplan, member, American College of Obstetricians and Gynecologists addiction expert group

Dr. Pat Marmion, an OB-GYN in southern Washington, says he helped coordinate efforts to file complaints with the university and the U.S. Department of Health and Human Services, which oversees the National Institutes of Health. An HHS spokesperson declined comment.

“We should be encouraging women who are pregnant to not use marijuana instead of incentivizing them to continue,” Marmion said.

Under U.S. law, research that involves humans must be approved by review boards to make sure participants’ rights and safety are protected.

Karen Moe, director of the university’s human subjects division, said authorities there investigated the critics’ concerns and concluded that most were unfounded. But she said they agreed to provide a handout on possible risks from marijuana use in pregnancy, not just links to similar information online, and also reworded recruitment materials to clarify that participants could quit using marijuana and still receive full payment.


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“From our standpoint the situation is essentially resolved and the study is good to go,” Moe said.

Dr. Mishka Terplan, a member of the American College of Obstetricians and Gynecologists’ addiction expert group, said that for years, the thalidomide scare “shut down all research of medications in pregnancy.” Not enough is known even about medications commonly prescribed for morning sickness, he said.

“We shouldn’t assume that because we classify something as illegal that it is shameful,” Terplan said. “And that because something is legal and prescribed, [then] it’s helpful.”

The National Institute on Drug Abuse is providing almost $1.5 million for three similar studies of marijuana use in pregnancy — at Washington University in St. Louis, at the University of Denver and at Kaiser Permanente in Northern California.


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“One of the big arguments about why this is unethical is that we already know the answers. That is not true,” said Susan Weiss, who oversees outside research for the institute. “We’re living in this very large social experiment and we need to learn from it.”

Leslie Siu, the businesswoman who used marijuana while pregnant, now lives in Denver, where pot is legal, and sells a marijuana-based spray. Siu said marijuana deserves to be studied “so we can get the right answers.”

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  • Lana Jane

    The critics against this study are the same critics who would be so fast to push pills on pregnant women. “Depressed? Anxious? Here, take these drugs, they’re safer than marijuana in moderation.” No…those drugs haven’t been around for thousands of years, and they’re synthetic. In other words, doctors are against marijuana use because they lose the kickback they earn from pushing drugs.

    • Serai 1

      I can’t get my head around them making a FAKE version of THC. Why?? Why not just give the people who need it the real thing? It’s bizarre. But I guess that’s what you get in a culture that persecutes people for having fun.

    • CNJ Creations


    • P.J. Rafter

      I couldn’t agree more ─ synthetic pharmaceuticals are slow-acting poisons and doctors are the pushers!

      Hippocratic oath, my a$$!

  • Serai 1

    Back in the early 90’s I roomed with a woman who was a hospital nurse. She also smoked weed. Didn’t do any other drugs like alcohol or tobacco. She got pregnant, but kept smoking weed. Everyone in the house (there were five roommates) eagerly awaited the birth and we all loved that baby. And she was GREAT. Probably the most alert, lively baby I’ve ever met. Started every development (opening eyes, recognizing images, sitting up, crawling, talking) earlier than expected for her size, which was normal. That was a baby that was HAPPY to be involved in life. So much for fear-mongering about weed!

  • CNJ Creations

    It really bothers me how much they push against these studies. When clearly so many women voluntarily use cannabis during pregnancy and go on to have happy and healthy babies. In fact, I used cannabis during my first trimester because it was the one thing that actually helped my nausea. Of course instead my doctor recommended against it and prescribed some harsh pill the pharmacy reluctantly filled and recommended I just do the b-6 vitamin. So I actually took a week and stopped the cannabis and just tried to b-6. Needless to say I went back to the cannabis. Thus far my baby has been doing VERY well.

  • Bill Lewis

    Lana Jane is right on target…anyone who says different is a liar!

  • Max J Ellis

    They currently prescribe Zofran for morning sickness which causes birth defects. Had my son’s mom used her prescription our son would have had health issues. Pot does nothing to the baby. 37+ years ago my mother smoked weed while pregnant, my brain function is fine. I’m fine.

    Also, someone in the article is quoted as saying “marijuana addicts,” that person sounds very I’ll-informed and should not be allowed to have an opinion on this issue at all.

  • Beyond safety issues and a myriad of studies linking products of combustion to low birth weight infants and premature births, the ethics of using any prescription or illicit drug that exposes a fetus in utero to potentially harmful impacts drives this debate! As a woman and as a physician I encourage pregnant women to consider use of topicals and transdermals that do not enter the blood supply. The research should focus on the potential benefits of legal hemp oils with FDA analyzed CBD content as an alternative to inhaled methods. It defies common sense logic why anyone with understanding of the medical, legal and industry impacts of “smoking weed” would promote use of inhaled methods in a pregnant woman.

    • Lana Jane

      They’re also studying edibles, not just smoking it.

  • VS Buxton

    A natural herb is demonized yet chemical-laden vaccines , not proven safe, are pumped into pregnant women and babys …