STAG3 and spontaneous abortion: In conclusion, our study presents a body of evidence showing that Stag3 is a master regulator of microtubule dynamics that maintains normal spindle assembly, proper chromosome alignment and correct kinetochore-microtubule attachment to prevent generation of aneuploid eggs, providing a new molecular determinant controlling oocyte development and helping dissect the molecular bases of infertility, miscarriage, early embryonic lethality and birth defects in humans.