Use of marijuana during pregnancy was associated with symptoms of nausea and vomiting and with use of prescribed antiemetics, according to a study presented Feb. 3 at the meeting sponsored by the Society for Maternal-Fetal Medicine. It’s unclear, however, whether the association suggests that pregnant individuals are using marijuana in an attempt to treat their symptoms or whether the marijuana use is contributing to nausea and vomiting – or neither, Torri D. Metz, MD, of the University of Utah Health in Salt Lake City, told attendees.
“Cannabis use has been increasing among pregnant individuals,” Dr. Metz said. “Reported reasons for use range from habit to perceived benefit for treatment of medical conditions, including nausea and vomiting.” She noted a previous study that found that dispensary employees in Colorado recommended cannabis to pregnant callers for treating of nausea despite no clinical evidence of it being an effective treatment.
”Anecdotally, I can say that many patients have told me that marijuana is the only thing that makes them feel better in the first trimester, but that could also be closely tied to marijuana alleviating their other symptoms, such as anxiety or sleep disturbances,” Ilina Pluym, MD, of the department of maternal-fetal medicine at the University of California, Los Angeles, said in an interview. ”In the brain, marijuana acts to alleviate nausea and vomiting, and it has been used successfully to treat nausea [caused by] chemotherapy,” said Dr. Pluym, who attended the abstract presentation but was not involved in the research. “But in the gut, with long-term marijuana use, it can have the opposite effect, which is what is seen in cannabinoid hyperemesis syndrome.”
Past research that has identified a link between cannabis use and nausea in pregnancy has typically relied on administrative data or self-reporting that are subject to recall and social desirability bias instead of a biomarker to assess cannabis use. This study therefore assessed marijuana use based on the presence of THC-COOH in urine samples and added the element of investigating antiemetic use in the population.
The study enrolled 10,038 nulliparous pregnant patients from eight U.S. centers from 2010 to 2013 who were an average 11 weeks pregnant. All participants completed the Pregnancy-Unique Quantification of Emesis (PUQE) tool at their first study visit and consented to testing of their previously frozen urine samples. The PUQE tool asks participants how often they have experienced nausea, vomiting, or retching or dry heaves within the previous 12 hours. A score of 1-6 is mild, a score of 7-12 is moderate, and a score of 13 or higher is severe.
Overall, 15.8% of participants reported moderate to severe nausea and 38.2% reported mild nausea. A total of 5.8% of participants tested positive for marijuana use based on THC levels in urine. Those with incrementally higher levels of THC, at least 500 ng/mg of creatinine, were 1.6 times more likely to report moderate to severe nausea after accounting for maternal age, body mass index, antiemetic drug use, and gestational age (adjusted odds ratio, 1.6; P < .001). An association did not exist, however, with any level of nausea overall. Those with higher creatinine levels were also 1.9 times more likely to report vomiting and 1.6 times more likely to report dry heaves or retching (P < .001).
About 1 in 10 participants (9.6%) overall had used a prescription antiemetic drug. Antiemetics were more common among those who had used marijuana: 18% of those with detectable THC had used antiemetics, compared with 12% of those without evidence of cannabis use (P < .001). However, most of those who used marijuana (83%) took only one antiemetic.
Among the study’s limitations were its lack of data on the reasons for cannabis use and the fact that it took place before widespread cannabidiol products became available, which meant most participants were using marijuana by smoking it.
Dr. Pluym also pointed out that the overall rate of marijuana use during pregnancy is likely higher today than it was in 2010-2013, before many states legalized its use. “But legalization shouldn’t equal normalization in pregnancy,” she added.
In addition, while the PUQE score assesses symptoms within the previous 12 hours, THC can remain in urine samples anywhere from several days to several weeks after marijuana is used.
”We’re unable to establish cause and effect,” Dr. Metz said, “but what we can conclude is that marijuana use was associated with early pregnancy nausea and vomiting.”
The findings emphasize the need for physicians to ask patients about their use of marijuana and seek to find out why they’re using it, Dr. Metz said. If it’s to treat nausea and vomiting of pregnancy, ob.gyns. should ensure patients are aware of the potential adverse effects of marijuana use in pregnancy and mention safe, effective alternatives. Research from the National Academy of Sciences has shown consistent evidence of decreased fetal growth with marijuana use in pregnancy, but there hasn’t been enough evidence to assess potential long-term neurological effects.
The research was funded by the National Institute on Drug Abuse and the National Institute of Child Health and Human Development. Dr. Metz and Dr. Pluym reported no disclosures.