Marijuana is the most commonly used illicit drug during pregnancy, and its use is rising. In 2002, it was estimated that 2.4 percent of pregnant women aged 18 to 44 used marijuana whereas almost 4 percent used in 2014. Aggregate data from 2002-2012 indicate that almost 15 percent were current marijuana users, however, the authors state that this number likely underestimates actual use because of underreporting and social desirability bias. The authors investigated trends of prenatal marijuana use from 2009-2016 using a large California health care system’s dataset.
The main study findings are: From 2009 to 2016, marijuana use based on self-report or urine toxicology among 279,457 pregnant women increased from 4 percent to 7 percent. Women were almost twice as likely to screen positive for marijuana use via urine drug tests versus self-report, strongly suggesting that marijuana use during pregnancy has been underestimated in self-reported surveys. Of concern, 22 percent of adolescents (aged <18) and 19 percent of young adults (aged 18-24) screened positive for marijuana use in 2016.
The authors conclude that it will be important to monitor marijuana trends, exposure timing, and birth outcomes because of its potential to impair fetal growth and development of the brain.