A new study published in the American Journal of Reproductive Immunology investigated whether abnormal increase or decrease of M1/M2 macrophages are observed in the deciduae of miscarriages with normal fetal chromosome (MN). This study obtained deciduae of 18 MN and 26 miscarriages with abnormal fetal chromosome (MA), along with deciduae from 15 other women whose pregnancies ended in induced abortions (IA), and endometriums at the mid-luteal phase from 19 non-pregnant women endomeriums of mid-luteal phases (EM). It was found that M1 macrophages, defined as CD68⁺ HLA-DR⁺ CD163^- cells, increased in MN compared with MA or IA. While M2 macrophages, defined as CD68⁺ HLA-DR^- CD163⁺ cells, increased in the deciduae of MA and IA compared with EM. On the otrher hand, this increase was not noted in the deciduae of MN. From the results of this study, it was inferred that M2 polarization is favorable for the maintenance of early stages of pregnancy.