Our findings thus support the hypothesis that early pregnancy, possibly through a decrease of PR positive luminal cells, leads to a decreased activation of the Wnt- signaling pathway and subsequent lower expression of the Wnt target Versican, which, by inhibiting the proliferation of mammary stem/progenitor cells, may be the reason for the lower incidence of subsequent breast cancer in these women. The gene discussed is PGR; the disease is breast carcinoma.