RationaleStudies investigating the risk of active tuberculosis (TB) in association with pregnancy have not been conclusive. We aimed to investigate this risk in a large retrospective register-based cohort study in Sweden.MethodsData from women of 15–49 years of age who had given birth in Sweden between 2005 and 2013 were extracted from the national childbirth register and linked to the national TB register. Cohort time was divided into three exposure periods: during pregnancy, six months (180 days) postpartum and time neither pregnant nor postpartum. We calculated incidence rates (IRs) per 100 000 person-years for each period and incidence rate ratios (IRRs) with IRs neither pregnant nor postpartum as the reference.ResultsThe cohort included 649 342 women, of whom 553 were registered as cases of active TB, 389 when neither pregnant nor postpartum, 85 during pregnancy and 79 when postpartum. Overall IRs were 9, 12 and 17 cases per 100 000 person-years, respectively, giving IRR 1.4, 95% CI 1.1–1.7 (during pregnancy) and IRR 1.9, 95% CI 1.5–2.5 (when postpartum). Stratification by TB incidence in country of origin showed that the increased risk was concentrated amongst women from countries with a TB incidence of 100 or higher, where IRs per 100 000 person-years were 137 (when neither pregnant nor postpartum), 182 (during pregnancy) and 233 (when postpartum).ConclusionWe show a significant increase in risk of active TB during both pregnancy and postpartum in women from high incidence countries and recommend TB screening in pregnant women belonging to this risk group.