VEGFA and spontaneous abortion: Given the delicate balance that promotes placentation under hypoxic conditions in normal early pregnancies, including successful angiogenesis and regulation of pro- and anti- angiogenic factors such as VEGF and sFlt1, our findings suggest an imbalance of pro and anti-angiogenic factors may be an early step in the pathophysiological process of miscarriage which, in turn, may be precipitated by differences in oxygen tension.