AbstractBackgroundEvidence of the associations between prenatal cannabis exposure and maternal, infant, and child health outcomes remains conflicting amid broad legalization of cannabis across Canada and 40 American states. A primary critical limitation of existing evidence lies in the non-standardized and crude measurement of prenatal cannabis exposure, resulting in high risk of misclassification bias. We developed a standardized tool to comprehensively measure prenatal cannabis use in

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... populations for research purposes.MethodsWe conducted a patient-oriented tool development and validation study using a six-step, bias-minimizing process. Following an environmental scan and critical appraisal of existing prenatal substance use tools, we recruited pregnant past- present- and non-cannabis users via targeted social media advertising and obstetric clinics in Alberta, Canada. We conducted individual in-depth interviews and cognitive interviewing in separate sub-samples, to develop and refine our tool. We assessed content, convergent and discriminant validity, internal consistency and 3-month test-retest reliability, and validated externally against urine THC bioassay at multiple timepoints in pregnancy.Results194 pregnant women participated. The 9-item Cannabis Exposure in Pregnancy Tool (CEPT) had excellent discriminant (Cohen's kappa=-0.27 to 0.15) and convergent (Cohen's kappa=0.72 to 1.0) validity; as well as high internal consistency (Chronbach's alpha = 0.92), and very good test-retest reliability (weighted Kappa=0.92, 95% C.I. [0.86 – 0.97]). The CEPT is valid against gold-standard urine THC bioassay (sensitivity 77%, specificity 100%) in preliminary analyses.InterpretationDeveloped for research purposes, the CEPT is a novel, valid and reliable measure of frequency, timing, dose, and mode of prenatal cannabis exposure, in a contemporary sample of pregnant women. Use of the CEPT can improve measurement accuracy, and thus the quality of research examining associations between antenatal cannabis use and maternal and child health outcomes.