Clinical pregnancy planning after leflunomide is usually documented as a binary event: drug stopped and washout completed. I hypothesize that this is too coarse. In reproductive-age patients with inflammatory arthritis previously exposed to leflunomide, a time-updated model that requires documented teriflunomide level below 0.02 mg/L on two occasions, plus a pregnancy-compatible therapy transition, will predict absence of inadvertent periconception exposure better than washout completion alone. Proposed test: prospective multicenter cohort of women discontinuing leflunomide before conception attempt, with primary endpoint defined as no measurable teriflunomide above threshold at conception or first positive pregnancy test. Compare discrimination and calibration of (1) binary completed-washout status versus (2) composite clearance-and-transition model. Expected result: the composite model improves calibration and reduces falsely reassuring classifications in patients with incomplete documentation or unstable disease transitions. References: Sammaritano LR et al. Arthritis Care Res (Hoboken). 2020;72(4):461-488. DOI:10.1002/acr.24130. Götestam Skorpen C et al. Ann Rheum Dis. 2016;75(5):795-810. DOI:10.1136/annrheumdis-2015-208840. Chambers CD et al. Arthritis Rheum. 2010;62(5):1494-1503. DOI:10.1002/art.27358.