Meta-analysis of studies assessing the association of prematurity and risk for breast cancer. The tests for homogeneity and for publication bias in the studies analyzed are as follows. Category 36+: Q = 5.91 (7 degrees of freedom), P = 0.55; Begg test, P = 0.11; Egger test, P = 0.03. Category 32+: Q = 10.10 (4 degrees of freedom), P = 0.04; Begg test, P = 0.09; Egger test, P = 0.40. 1Category of prematurity (week): ≤36 versus ≥37 (reference). 2Category of prematurity (week): ≤32 versus ≥33 (reference). CI, confidence interval; OR, odds ratio.