Pregnancy: A risk for developing tuberculosis? A national cohort and self-controlled case series study using UK primary care data

Introduction: Tuberculosis (TB) incidence has increased in the UK over the last decade. The study of TB in pregnancy is important because of adverse outcomes in mother and child. The aim of this study was to analyse the epidemiology of TB in pregnancy in the UK, and establish, whether pregnancy is an independent risk factor for TB in order to inform prevention and early detection strategies. Methods: Using a cohort based on the UK General Practitioner Research Database (GPRD), incidence rates (IR) and rate ratios (IRR) of TB events in three time periods were compared using Poisson regression: pregnancy, a period of 6 months post-partum, and outside of pregnancy. In addition TB risk was calculated using a nested self-controlled case series (SCCS) analysis which implicitly adjusts for time-bounds covariates. Results: Combined pregnancy and post-partum TB rates (15.4 per 100,000 person years, py) were significantly higher than rates outside of pregnancy (9.1 per 100,000 py, p=0.02). Compared to risk outside of pregnancy, TB risk was not significantly increased during pregnancy (IRR 1.29, CI 0.82-2.03), but significantly increased post-partum (IRR 1.95, CI 1.24-3.07), adjusting for age, region and deprivation. These observations were confirmed in the SCCS (IRR 1.62, CI 1.01-2.58 and 1.03, CI 0.64-1.65). Conclusions: There is a significantly increased post-partum TB risk and this is very likely pregnancy-related, but occurs post-partum due to administrative, diagnostic or immunological delays. Our results can be used to raise clinicians9 awareness and inform targeted public health policy measures to minimise this risk.