The Sialyl Tn antigen test was described by Kobayashi and colleagues, who showed that monoclonal antibodies TKH-2, MA54, B72.3, and CC49 react with meconium and amniotic fluid-derived mucin.6 TKH-2 has the ability to detect the lowest concentration of the antigen. Sialyl is a mucin-type glycoprotein that originates in fetal and adult intestinal and respiratory tracts. It is a major component in meconium (10% by weight) and is also present in clear amniotic fluid. Using a sensitive anti-mucin antibody TKH-2, the authors found no difference in the serum levels of Sialyl Tn antigen in pregnant patients throughout gestation or in early postpartum period when compared with non-pregnant controls. In contrast, the antigen concentrations were significantly elevated in patients with AFE. The monoclonal antibody TKAH-2 may eventually prove useful in rapid, non-invasive diagnosis of AFE