Infantile hemangioma(IH) is one of the most common benign tumors in infants characterized by occurrence within a few weeks after birth,rapid growth during the first year and spontaneous involution over a period of several years.Despite the high incidence rate of 5%-10% in infants of mixed European descent,detailed pathogenesis of IH remains elusive.Recent studies have indicated multipotential stem cells derived from hemangioma tissue(HemSCs) could recapitulate human infantile hemangioma in immunodeficient mice.Considering the effect of progesterone on regulation of cytokines and growth factors in endometrium as well as the inhibition of immune response,using progesterone during pregnancy might help the HemSCs escape from the immune response and reside in the tissue of embryo by the aid of increased MMPs and decreased TIMPs,then proliferation was stimulated by increased growth factors like VEGF and bFGF.Thus,IH is potentially produced.