In a recent study, Tsuda et al. 95 found that the frequency of CD4+CD45RA-CD25+CD127low/- effector Tregs (also defined as one of memory Treg subsets) among CD4+CD25+CD127low/- total Tregs in decidua were significantly lower in miscarriage with normal chromosomal karyotyped embryo than 1st trimester normal pregnancy. Here, CD4 is linked to spontaneous abortion.