Multiple types of exogenous microparticles coexist in the early human decidua and placental villi

• This study demonstrates the presence of multiple exogenous microparticles (EMP) types in early human placental tissue, with predominant localization in placental villi, primarily consisting of carbon-rich and iron-rich particles. • PM showed higher accumulation and larger particle sizes in placental villi compared with decidual tissue. • Detailed information about EMP present in human placental villi was obtained for the first time via in situ AFM-IR and STEM-EDXS. • No significant differences were observed in EMP accumulation between placental tissues from induced and spontaneous abortions, EMP abundance was associated with maternal clinical indicator. Maternal exposure to exogenous microparticles (EMP) during pregnancy is associated with multiple adverse birth outcomes, yet evidence for its accumulation in early placental tissues remains limited. This study investigates the accumulation of EMP in early placental villi and decidua, exploring its association with miscarriage. A total of 40 pregnant women undergoing abortion (20 spontaneous and 20 induced) were enrolled. Placental villi and decidual tissues were collected under strict quality control, subjected to digestion and filtration, and analyzed using Raman spectroscopy. In addition, combined spectroscopic and electron microscopy techniques were employed for in situ detection of particles within the placental villi. Among 174 identified EMP, 68.4% were found in placental villi, primarily consisting of carbon-rich and iron-rich particles, with three microplastics also detected. Notably, EMP in villi exhibited larger mean size (11.37 ± 9.39 μm) and greater abundance (19.3 ± 19.4 items/g) compared to decidua. Additionally, in situ images of EMP in placental villi and their chemical composition were revealed. Despite no significant differences in EMP accumulation characteristics between the two groups, placental EMP abundance was significantly correlated with maternal platelet count and serum β‑hCG levels ( P < 0.05). This study demonstrates that EMP from ambient can translocate to placental villi and decidua, thereby directly exposing the placenta and fetus. Given the established associations between air pollution and adverse birth outcomes, the effects of such exposures on placental function and fetal development remain to be fully elucidated.