(HealthDay)—More than twice as many pregnant 12- to 17-year-olds use marijuana as their nonpregnant peers, and significantly more use the drug than pregnant women in their 20s, according to a letter published online April 17 in the Annals of Internal Medicine.

The new findings stem from a 2002 to 2015 National Survey on Drug Use and Health that explored marijuana use among 410,000 females ages 12 to 44. About 14,400 survey participants were pregnant at the time of polling. All participants were asked about their pregnancy status and marijuana use during the prior month. Final tallies were based on self-reports.

"We found that almost 4 percent of [all] pregnant women reported marijuana use in the past month," study author Nora Volkow, M.D., director of the U.S. National Institute on Drug Abuse, told HealthDay. Marijuana use was much lower for adults 26 and older (less than 2 percent) than for those 18 to 25 years old or teens 12 to 17. Blacks were more likely than whites or Hispanics to use marijuana during pregnancy. Marijuana use in pregnancy was more common during the first trimester versus the second and third trimesters.

"Reports suggest that some are using marijuana as an antiemetic, particularly during the first trimester," the authors write. "Evidence for the effects of marijuana on human prenatal development is limited; however, research suggests that concern is warranted and that, even with the current uncertainty about 's influence on human neurodevelopment, clinicians should exert caution by not recommending this for pregnant patients."