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PURPOSE The aim of this study was to assess maternal risk factors and perinatal characteristics of patients with anorectal malformations (ARM) in Sweden. METHODS Population-based case-control study including all patients with ARM born in Sweden 1973-2014. Patients were identified from the Swedish National Patient Register, and data on possible maternal risk factors and perinatal characteristics were obtained from the Swedish Medical Birth Register. The association between study variables and ARM was analyzed using conditional logistic regression. RESULTS 1167 patients and 5835 controls were analyzed. Patients with ARM were more often prematurely born (<35 weeks: OR 4.81 95% CI 3.42-6.75, 35-36 weeks OR 2.96 95% CI 2.13-4.11) or small for gestational age (SGA) (OR 3.82 95% CI 2.66-5.50). Maternal BMI ≥30 was associated with an increased risk for ARM (OR 1.42; 95% CI 1.08-1.86). Maternal smoking ≥10 cigarettes daily was associated with ARM only in patients without associated malformations (OR 1.67 95% CI 1.08-2.58). CONCLUSIONS Maternal obesity is a possible risk factor for ARM. Prematurity and SGA was more common among ARM patients. Maternal smoking may be a risk factor of ARM in patients without associated malformations. LEVEL OF EVIDENCE III.