Publish date: April 28, 2019By M. Alexander Otto


BALTIMORE – Marijuana is a not a good idea during pregnancy, and it’s an even worse idea when women are being treated for opioid addiction, according to an investigation from East Tennessee State University, Mountain Home.

Marijuana use may become more common as legalization rolls out across the country, and legalization, in turn, may add to the perception that pot is harmless, and maybe a good way to take the edge off during pregnancy and prevent morning sickness, said neonatologist Darshan Shaw, MD, of the department of pediatrics at the university.

Dr. Shaw wondered how that trend might impact treatment of opioid use disorder (OUD) during pregnancy, which has also become more common. The take-home is that “if you have a pregnant patient on medically assistant therapy” for opioid addition, “you should warn them against use of marijuana. It increases the risk of prematurity and low birth weight,” he said at the Pediatric Academic Societies annual meeting.

He and his team reviewed 2,375 opioid-exposed pregnancies at six hospitals in south-central Appalachia from July 2011 to June 2016. All of the women had used opioids during pregnancy, some illegally and others for opioid use disorder (OUD) treatment or other medical issues; 108 had urine screens that were positive for tetrahydrocannabinol (THC) at the time of delivery.

Infants were born a mean of 3 days earlier in the marijuana group, and a mean of 265 g lighter. They were also more likely to be born before 37 weeks’ gestation (14% versus 6.5%); born weighing less than 2,500 g (17.6% versus 7.3%); and more likely to be admitted to the neonatal ICU (17.5% versus 7.1%).

On logistic regression to control for parity, maternal status, and tobacco and benzodiazepine use, prenatal marijuana exposure more than doubled the risk of prematurity (odds ratio, 2.35; 95% confidence interval, 1.3-4.23); tobacco and benzodiazepines did not increase the risk. Marijuana also doubled the risk of low birth weight (OR, 2.02; 95% CI, 1.18-3.47), about the same as tobacco and benzodiazepines.

The study had limitations. There was no controlling for a major confounder: the amount of opioids woman took while pregnant. These data were not available, Dr. Shaw said.

Neonatal abstinence syndrome was more common in the marijuana group (33.3% versus 18.1%), so it’s possible that women who used marijuana also used more opioids. “We suspect that opioid exposure was not uniform among all infants,” he said. There were also no data on the amount or way marijuana was used.

Marijuana-positive women were more likely to be unmarried, nulliparous, and use tobacco and benzodiazepines.

There was no industry funding for the work, and Dr. Shaw had no disclosures.