Similarly, the IL1A GWA signal showed a near genome-wide significant (P = 4.4 × 10−7; Phet = 0.76) association with all (Table 2) endometriosis and the signal was comparable for Grade B (P = 5.1 × 10−7; Phet = 0.65) cases (Supplementary Table S2), with no evidence of heterogeneity in allelic associations (Phet = 0.55). Here, IL1A is linked to endometriosis.