When the placenta has clots present either inside it (placental thrombosis) or under it (sub placental clots), it means that a portion of the placenta has been damaged, resulting in less efficient blood flow to and from the mother. In such cases, the fetus cannot receive the necessary nutrients and ultimately, the necessary oxygen for healthy development. Fetuses with such placentas are at risk for growth failure, preterm delivery, brain damage and even death. The risk for brain damage and death is highest during labor due to the additional stress imposed by the labor process.
