Smoking marijuana during pregnancy can cause health problems in the neonate. The detection of exposure can guide treatment to meet the short- and long-term medical and social needs. Umbilical cord tissue was analyzed for 11-nor-delta-9-carboxy-tetrahydrocannabinol (THC-COOH) by gas chromatography-mass spectrometry (GC-MS), and compared with ultra-sensitive enzyme-linked immunosorbent assay (ELISA) and liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS). Fortified extracts of drug-free cord tissue were used to determine the sensitivity and specificity of the LC-TOF-MS and ELISA assays, and 16 de-identified patient specimens previously analyzed by GC-MS were tested for THC-COOH by both methods. The cutoffs were 0.050 ng/g for the GC-MS assay, 0.1 ng/g for the ELISA assay and 1 ng/g for the LC-TOF-MS assay. Twelve specimens were negative by all three methods. Seven specimens were positive by GC-MS with concentrations from 0.066 to 6.095 ng/g. ELISA and LC-TOF-MS did not detect one specimen that was positive by GC-MS. LC-TOF-MS missed one specimen that was detected by GC-MS and ELISA. Five positive specimens were detected by all three methods. These results were consistent with the cutoff for each method. No false positives were detected by LC-TOF-MS or ELISA. Umbilical cord tissue is a viable specimen for the detection of in utero marijuana exposure. ELISA and GC-MS were more sensitive than LC-TOF-MS for the detection of THC-COOH in cord tissue, with the GC-MS method providing superior sensitivity.