Umbilical Cord Drug Screening in Multiple Births: Experience from a Reference Laboratory and Academic Medical Center

The objective of this study was to review the results of umbilical cord drug screening in twins and triplets (multiples) to compare drug(s) and/or drug metabolite(s) detected. Results that did not agree between multiples were considered mismatched and were investigated. A retrospective analysis was conducted using de-identified data from a national reference laboratory, and results were compared with data from an academic medical center, where detailed medical chart review was performed. Umbilical cord was analyzed for stimulants, sedatives, opioids, and other drugs and metabolites. For the reference laboratory dataset, 23.3% (n=844) of 3,616 umbilical cords from twins (n=3,550) or triplets (n=66) were positive for one or more drugs and/or metabolites. Of these, mismatched results were identified for thirty-seven sets of twins (2.1%) and no sets of triplets. The most frequent mismatches were found in opioids (n=24), with morphine (n=5) being the most mismatched of any single analyte in the panel. Mismatches for the marijuana metabolite 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (9-COOH-THC) in the reference laboratory dataset occurred in six of 737 sets of twins (0.8%) and no triplets. For the academic medical center dataset, 21.9% (n=57) of 260 umbilical cords tested positive for one or more drugs and/or metabolite(s). Of these, 4 mismatches (3.2%) were identified, including 9-COOH-THC (n=2), phentermine (n=1), and oxycodone (n=1), all involving twins. All involved cases where the discrepant analyte was likely present in the negative twin but either slightly below reporting cutoff threshold, or failed analytical quality criteria. Mismatched results of umbilical cord drug screening occur in less than 4% of twins and most often occur when the analyte is slightly above the reporting cutoff in just one infant.