A retrospective study of five Massachusetts birthing hospitals examined toxicology testing performed at delivery solely because of a history of cannabis use. Among 614 mother–infant pairs tested for that reason, eight (1.3%) had an unexpected positive result for another substance, seven (1.1%) had false-positive results, and only one test changed clinical management. The group selected for testing disproportionately included younger, Black, Hispanic or Latino, and publicly insured patients. The findings question the clinical value of cannabis-only testing indications and raise concerns about unequal testing and unintended consequences.
