M1 macrophages decrease in the deciduae from normal pregnancies but not from spontaneous abortions or unexplained recurrent spontaneous abortions

To investigate the M1/M2 polarity of macrophages in the endometrium among different menstrual cycles, normal and abnormal pregnancies, and unexplained recurrent spontaneous abortions (RSAs). Methods: Endometrial tissue was obtained from 43 patients undergoing hysterectomy, either in the follicular phase (Group 1, n = 23) or in the luteal phase (Group 2, n = 20). In addition, decidual tissue was obtained from 53 pregnant women during the first trimester, either of normal pregnancies (Group 3, n = 12) or abnormal pregnancies (Group 4: spontaneous abortions, n = 20; Group 5: unexplained RSA, n = 21). Using immunofluorescence to examine the M1 and M2 macrophages in the endometrium and deciduae from cases with different menstrual phases and various pregnancy outcomes, respectively, we endeavored to learn the possible pathophysiology of abortions. Results: M1 macrophages were abundant in the deciduae of spontaneous abortions and unexplained RSA, whereas the frequency of M2 macrophages was significantly higher in the endometrium of luteal phase and normal pregnancies. Conclusion: M2 polarization is important for early successful pregnancies in humans.