Meconium aspiration is a common complication of childbirth in a newborn. Meconium is the first stool passed by a newborn; it’s dark green, very sticky and thick. If a baby is stressed in utero, even for a short time, meconium may be passed into the amniotic fluid that surrounds the baby. If the baby takes a breath before birth, meconium can be sucked down into the lungs.
Initial Side Effects
Meconium aspiration occurs in approximately 15 percent of deliveries, and in over 90 percent of cases, the symptoms last only a short time. A baby who inhales meconium may have transient respiratory distress, with rapid or slow breathing, nasal flaring, grunting, cyanosis (a bluish tint to the skin that indicates low oxygen levels) or no breathing effort. The baby may be initially floppy, with poor muscle tone, or limp. Most babies respond well to initial oxygen therapy and require no more than short term oxygen administration, but a small number progress to meconium aspiration syndrome, or MAS.
Serious Side Effects
MAS is a life threatening complication of meconium aspiration and needs prompt expert care from experienced neonatologists. Signs of meconium aspiration syndrome are small and large airway blockage, edema and inflammation in the lungs, collapsed lungs and infiltrates on chest x-ray, and a “barrel chest” appearance from trapped air. Aspiration pneumonia can develop and need ventilator treatment.
MAS can also cause persistent pulmonary hypertension (PPH) which leads to persistent fetal circulation (PFC). PPH is caused by high pressure in the pulmonary artery, the blood vessel that leads to the lungs. Vasoconstriction of the artery can be caused by respiratory acidosis caused by low oxygen levels. Because the pressure is high in the pulmonary artery, blood flows through the area of lesser resistance and bypasses the lungs. This leads to persistence fetal circulation, or PFC.
PFC means that blood flow is still traveling through the heart in a fetal pattern, which, because oxygen is supplied through the umbilical cord rather than through the lungs, bypasses the lungs and is shunted through the patent (open) ductus arteriosus from one side of the heart to the other. After birth, the ductus arteriosus normally closes, and oxygen enters the bloodstream through the lungs. In babies with PFC, the ductus arteriosus stays open, and blood is shunted from one side of the heart to the other without being properly oxygenated. PFC results in a severe lack of oxygenation.
PPH and PFC require sophisticated neonatology treatment. Some of the treatments used to treat PPH and PFC are mechanical ventilation, with a breathing tube, administration of nitric oxide, a drug that relaxes constricted blood vessels and improves blood flow to the lungs, or extracorporeal membrane oxygenation (ECMO). ECMO works similarly to a heart lung bypass machine; it allows blood to be oxygenated outside the body and then returned.
Long Term Side Effects
Around 10 percent of babies who develop MAS don’t survive. Brain damage from lack of oxygen is a possible long term side effect. Children who survive MAS may be more likely to develop asthma.