Maternal marijuana use and neonatal outcome: uncertainty posed by self-reports

To assess the validity of self-reported marijuana use during pregnancy, this study randomly allocated pregnant women into a group who were told their urine would be tested for marijuana, alcohol, and other drugs and another group not so tested. Women told they would be tested reported more marijuana use during pregnancy than did untested women. Moreover, urine assays identified more women who used marijuana during pregnancy than were willing to admit it in the interview even after being told their urine would be tested. No differences in reported drinking or cigarette smoking during pregnancy were found between tested and untested women.