Dark green, sticky mucus normally found in infants' intestines. It is the first stool passed by the newborn. Meconium is a mixture of amniotic fluid, bile and secretions from the intestinal glands. Passage of meconium within the uterus before birth can be a sign of fetal distress. Meconium is very irritating to the lungs. If there is a possibility that an infant may have thick meconium in the lungs, the doctor inserts a tube into the trachea and suctions out the loose meconium. This tube, called an endotracheal tube, can also be used to help an infant breathe after the meconium has been removed.