TNF and Sacroiliac arthritis: In univariate analyses, OR for breastfeeding history with TNFa inhibitor usage was 0.364 (95% CI: 0.113–1.173, p = 0.091), OR with sacroiliitis was 0.308 (95% CI: 0.105–0.908, p = 0.033) and OR with comorbidity was 0.359 (95% CI: 0.155–0.835, p = 0.017) (Table 3).