TMEM43 and breast cancer: Similarly, among women with a first birth >23 years, the association between high LUMA methylation levels and breast cancer risk was increased by greater than 150%; whereas among women with a first birth ≤23 years, the LUMA methylation-breast cancer association was increased by only 32% (multiplicative interaction p value = 0.02) No modification of the LINE-1 methylation-breast cancer association was observed by any of the four reproductive characteristics considered.