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 (<16 weeks' gestation) self-reporting marijuana use MEASUREMENTS: Participants completed a written self-report survey and provided biospecimens at <16 weeks' gestation (n=46), 18-22 weeks' gestation (n=43), 32-36 weeks' gestation (n=39) and delivery (n=37). Self-reported marijuana use frequency was calculated based on past-month days of use multiplied by number of daily uses. Maternal urine and sera were tested for presence (>5ng/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 seven to 15 weeks' gestation, 87% had ongoing use by self-report, or positive urine or serum. The majority (33 [66%]) stopped using prior to 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 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (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.