Sometimes in mature newborns the first stools (meconium) is released in the uterine cavity. The amniotic fluid is green and after some time the amniotic sac and tissues of the fetus are also stained. The meconium has strong vasoconstriction effects on the umbilical vessels and decreases blood flow into the tissues of the newborn. Amnial epithelium degenerates and gets necrotic in several hours. The newborn may breathe the amniotic fluid containing the meconium (the meconium aspiration syndrome), that damage the pulmonary tissue and clinically manifests as respiratory distress of the newborn.
Fetal surface of the placenta is coloured to green or green-brown by the meconium.
Placenta coloured by meconium, stillborn child: Placenta, meconial discoloration, Macro, autopsy (72072)
Degenerative changes in amnial epithelium, necrosis of the epithelium, macrophages with meconium pigment: