Increased risk of active tuberculosis during pregnancy and postpartum: a register-based cohort study in Sweden

Rationale Studies investigating the risk of active tuberculosis (TB) in association with pregnancy have not been conclusive. We aimed at investigating this risk in a large retrospective register-based cohort study in Sweden. Methods Data from women 15–49 years of age who had given birth in Sweden 2005–2013 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 postpartum, and time neither pregnant nor postpartum. We calculated incidence rates (IR) per 100 000 person-years for each period, and incidence rate ratios (IRR) with IR neither pregnant nor postpartum as reference. Results The cohort included 649 342 women, of whom 553 were registered as cases of active TB: 389 when neither pregnancy nor postpartum, 85 during pregnancy and 79 during postpartum. Overall IR were 9, 12 and 17 cases per 100 000 person-years respectively, giving an incidence rate ratio (IRR) of 1.4 (95% CI 1.1–1.7) during pregnancy and 1.9 (95% CI 1.5–2.5) postpartum. Stratification by TB incidence in country of origin showed that the increased risk was concentrated to women from countries with a TB incidence of 100 or higher where incidence rates per 100 000 person-years were 137 when neither pregnancy nor postpartum, 182 during pregnancy and 233 postpartum. Conclusion We 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.