Quantification of prenatal marijuana use: evaluation of the correlation between self-report, serum, urine and umbilical cord assays among women delivering at two urban Colorado hospitals

BACKGROUND AND AIMS To estimate during pregnancy correlations between frequency of self-reported use of marijuana and quantified marijuana metabolite in biospecimens including urine, sera and umbilical cord homogenate. DESIGN Prospective cohort. SETTING Two urban hospitals in Colorado with legal recreational and medicinal marijuana. PARTICIPANTS Pregnant women ( 5 ng/mL) of 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH). Liquid chromatography tandem mass spectrometry quantified THC-COOH in umbilical cord homogenate (ng/g). Last marijuana use by any measure was recorded to evaluate the time frame over which THC-COOH remains detectable (>0.10 ng/g) in cord. FINDINGS From December 2017 through May 2019, 51 pregnant women enrolled, and 46 were included in analyses (2 withdrew and 3 had a spontaneous abortion). The majority were normal weight, White or Black race, and insured by Medicaid. At the time of enrollment between 7 to 15 weeks' gestation, 87% had ongoing use by self-report, or positive urine or serum. The majority (33 [66%]) stopped using before delivery. Sera and urine results were strongly correlated with self-reported use frequency (Spearman correlation coefficient [r] range 0.70-0.87 across visits, P < 0.001), and with each other. There was only one positive cord result when use stopped before 22 weeks. Frequency of self-reported marijuana use at delivery had strong correlation with quantified cord THC-COOH (r = 0.80, 95% CI = 0.62-0.89). CONCLUSIONS Quantified umbilical cord THC-COOH appears to strongly correlate with frequency of maternal marijuana use in the last month of pregnancy. Earlier use can be measured by either quantitative urine or serum assay.