Mammographic density, parity and age at first birth, and risk of breast cancer: an analysis of four case-control studies.
Woolcott CG, Koga K, Conroy SM, Byrne C, Nagata C, Ursin G, Vachon CM, Yaffe MJ, Pagano I, Maskarinec G. Mammographic density, parity and age at first birth, and risk of breast cancer: an analysis of four case-control studies. Breast Cancer Res Treat. 2012 Apr; 132(3):1163-71.