Detection of microchimerism in menstrual blood: a proof-of-concept study including 86 women.

RESEARCH QUESTION: Can microchimerism be detected in menstrual blood, and is it associated with recurrent pregnancy loss (RPL) or infertility? DESIGN: Exploratory cross-sectional study including 48 healthy women (controls), 30 women with RPL, and eight women with infertility. All participants collected menstrual blood during the first 48 h of one menstrual cycle. A peripheral blood sample was collected on cycle day 3. Peripheral blood mononuclear cells and menstrual blood mononuclear cells were isolated by density gradient centrifugation. In total, 287 samples from 86 women were examined for microchimerism with a Y-chromosome marker (DYS14) and the indel method. Additionally, 100 buccal swabs from male partners (n = 66) and live children (n = 34) were analysed for microchimerism. RESULTS: Microchimerism was detected in menstrual blood in a proportion of women in each study group, and aditionally, in peripheral blood with the exception of nulliparous homosexual women. The prevalence of microchimerism detected with DYS14 was higher in menstrual blood compared with peripheral blood for nulliparous heterosexual controls [75% (15/20) versus 4.8% (1/21)], women with primary RPL [53.3% (8/15) versus 6.3% (1/16)], and women with infertility [62.5% (5/8) versus 0% (0/7)]. These comparisons were not tested formally. The prevalence of microchimerism in menstrual blood detected by DYS14 and indels was similar in both condom users and non-users among nulliparous heterosexual controls. CONCLUSION: Microchimerism was detected in menstrual blood in all groups of women, irrespective of parity, and cannot be explained by sperm remains alone. The higher prevalence of DYS14-detected microchimerism in menstrual blood compared with peripheral blood for some study groups could reflect differing accumulation of microchimerism.