In a retrospective study of 501 neonates with potential in utero substance exposure, the drug detection performance of a commercially available umbilical cord tissue toxicology test was evaluated against a commercially available gold-standard meconium toxicology test. Drugs detected in paired MEC and UCT samples were often discordant.According to the 2016 National Survey on Drug Use and Health, nearly 20% of pregnant women aged 15-44 in the United States are estimated to have used alcohol, tobacco, or other illicit drugs during their pregnancy (1). Accurate assessment of substance exposure has implications for both the infant and mother (2-5). The American College of Obstetrics and Gynecology and the American Academy of Pediatrics recommend that screening of substance use in pregnancy be universal to avoid bias and utilize a standardized screening tool (eg, 4Ps or CRAFFT) (5,6).