CD4 and spontaneous abortion: In women with both uRPL and sporadic miscarriages, abnormalities in the normal function exerted by Tregs in uncomplicated pregnancies have been identified including: (1) higher numbers of Tregs from women with uRPL than normally fertile women were required to inhibit proliferation of CD4+CD25- effector cells in response to paternal allostimulation [56], and (2) the Helios+ Tregs—a supposed functionally active subset [174]—are reduced in the decidua of women with sporadic miscarriage with normal embryo karyotype [165].