Validity of Self-reported Cannabis Use Among Pregnant Females in Northern California.

ABSTRACT

BACKGROUND: Most clinical and epidemiologic estimates of prenatal cannabis use are based on self-report, and the validity of self-reported cannabis use has not been examined in a large, representative population of pregnant women. We determined the validity of self-reported prenatal cannabis use and predictors of nondisclosure using data from Kaiser Permanente Northern California's (KPNC) healthcare system with universal prenatal cannabis screening during prenatal care. METHODS: Validation study using data from 281,025 pregnancies in KPNC among females aged ≥11 years who completed a self-administered questionnaire on prenatal cannabis use and a cannabis urine toxicology test from 2009 to 2017. We calculated sensitivity, specificity, positive predictive value, and negative predictive value of self-reported prenatal cannabis use using urine toxicology testing as the criterion standard, and sensitivity of urine toxicology testing using self-reported use as the criterion standard. We compared sociodemographics of those who disclosed versus did not disclose prenatal cannabis use. RESULTS: Urine toxicology testing identified more instances of prenatal cannabis use than self-report (4.9% vs 2.5%). Sensitivity of self-reported use was low (33.9%). Sensitivity of the toxicology test was higher (65.8%), with greater detection of self-reported daily (83.9%) and weekly (77.4%) than monthly or less use (54.1%). Older women, those of Hispanic race/ethnicity, and those with lower median neighborhood incomes were most likely to be misclassified as not using cannabis by self-reported screening. CONCLUSIONS: Given that many women choose not to disclose prenatal cannabis use, clinicians should educate all prenatal patients about the potential risks and advise them to quit cannabis use during pregnancy.