Meconium aspiration syndrome: historical aspects

Abstract

The meconium aspiration syndrome (MAS) is a common problem that continues to concern perinatologists and neonatologists. MAS is defined as respiratory distress in an infant born through meconium-stained amniotic fluid (MSAF) whose symptoms cannot be otherwise explained. This disorder may be life threatening, complicated by respiratory failure, pulmonary air leaks and persistent pulmonary hypertension. Approaches to the prevention of MAS have changed over time with collaboration between obstetricians and pediatricians forming the foundations for care. This report details the management of babies delivered with associated MSAF before the accumulation of evidence for best practice through appropriately powered, prospective randomized controlled trials.

Meconium aspiration syndrome: challenges and solutions

“…It first appears in fetal intestine by approximately the 10th week of gestation and moves to colon by the 16th week. 2 Under normal circumstances, passage of meconium from the fetus into amnion is prevented by the lack of intestinal peristalsis due to low motilin levels, tonic contraction of anal sphincter, and a terminal cap of viscous meconium. 10 Transient parasympathetic neural stimulation because of head or cord compression, higher motilin levels, and increasing cholinergic innervation with advancing gestational age accounts for higher incidence of MSAF in term and post terms.…”

Respiratory distress syndrome of the preterm neonate — placenta and necropsy as witnesses

“…We know that control of fetal meconium passage depends on hormonal and parasympathetic neural maturation and is more common after 34 weeks gestation [13]. The exact mechanisms for in utero passage of meconium remain unclear, but fetal distress and vagal stimulation are two probable factors.…”

“…The exact mechanisms for in utero passage of meconium remain unclear, but fetal distress and vagal stimulation are two probable factors. Also, the passage of meconium below 34 weeks gestation may represent bilious reflux secondary to intestinal obstruction, and an aspiration into the airways may occur [13].…”

Risk Factors and Clinical Follow-Up Features of Meconium Aspiration Syndrome

“…15-20% of babies who develop MAS also develop persistent pulmonary hypertension (7). It is important to provide adequate respiratory support and acid-base balance in the treatment of pulmonary hypertension.…”

“…Regardless of other symptoms pointing to breathing difficulty in neonatal babies with MBAS, meconium aspiration syndrome is defined by the presence of early tachypnea, intercostal-subcostal retractions, respiratory distress symptoms such as cyanosis, crackles or rhonchi in lung auscultation, patchy infiltration on chest x-ray, and excessive aeration (7). MAS criteria according to severity are as follows: [1] Mild MAS: 40% less oxygen requirement within less than 48 hours; [2] Moderate MAS: oxygen requirement more than 40% for at least 48 hours regardless of any air leakage; [3] Severe MAS: need for mechanical ventilation for more than 48 hours often accompanied by persistent pulmonary hypertension (8).…”