Fetal inhalation of meconium in utero during episodes of severe fetal hypoxia or with the first few breaths after birth. Symptoms and signs, which occur to varying degrees, include respiratory distress, tachypnea, rales, and wheezes throughout the lung fields. Chest x-ray examination may show areas of increased density from the aspirated meconium, evidence of chemical pneumonitis, as well as areas of atelectasis caused by bronchiolar obstruction and collapse of alveoli distally. A pneumothorax also may occur from the ballvalve effect of meconium obstruction in the small bronchioles. These complications can produce hypoxia, acidosis, respiratory failure, persistent fetal circulation, and persistent pulmonary hypertension of the newborn (PPHN).
The inhalation of meconium, the initial stool of a newborn, by a fetus or infant, leading to the obstruction of air passages and hindrance of lung expansion.