The clinical significance of absent subchorionic fibrin in the placenta

Patchy fibrin is normally present beneath the chorionic plate of the placenta. The present study attempted to determine whether it has any clinical significance. In 31,622 placentas the amount of this fibrin was related to markers of fetal activity. Fibrin was often absent when the markers indicated hypoactivity. The markers of fetal hypoactivity were neonatal hypotonia, neonatal lethargy, the presence of Down's syndrome, and a short umbilical cord. Umbilical cord length is strongly influenced by tension applied to it by fetal movements--the fewer the movements, the shorter the cord. Children with no subchorionic fibrin subsequently had increased frequencies of cerebral palsy and low intelligence quotient values. Children who were hyperactive at one year of age had increased levels of subchorionic fibrin, which suggests that they were hyperactive before birth. All of these findings raise the possibility that normal fetal movements sometimes traumatize the placenta, which leads to fibrin deposits beneath its surface.