Discordant Umbilical Cord Drug Testing Results in Monozygotic Twins.

Our laboratory received segments of umbilical cord that originated from identical twins for routine toxicology analysis. The specimens were analyzed multiple times by liquid chromatography tandem mass spectrometry. The umbilical cord from newborn #1 was positive for hydromorphone only (1.06 ng/g), and the umbilical cord from newborn #2 was positive for hydromorphone (0.81 ng/g) and benzoylecgonine (5.41 ng/g). The hydromorphone results are consistent with maternal administration of hydromorphone; however, the cause of the discrepant benzoylecgonine results in the umbilical cords from the identical twins is unknown.