Risk factors for early and late onset of respiratory symptoms in babies born through meconium

We sought (1) to identify risk factors for meconium aspiration syndrome (MAS) among infants born to women whose labors were complicated by thick-consistency meconium-stained amniotic fluid (MSAF), and (2) to determine whether risk factors and infant prognosis differ according to the time of onset of respiratory distress. We performed a secondary analysis of a multicenter randomized trial of amnioinfusion (AI) for the prevention of MAS among women with thick-consistency MSAF. MAS was defined as onset of respiratory distress requiring oxygen supplementation within the first 4 hours of life. Patients with respiratory symptoms with onset at >or=4 hours were treated as a separate outcome category, "late-onset respiratory distress." We developed peripartum and intrapartum regression models to identify the risk of MAS and its subgroups. A tracing with marked abnormalities was a significant risk factor for moderate/severe MAS, but not for mild MAS or for late-onset respiratory distress. Meconium below the vocal cords and need for resuscitation immediately after birth were risk factors for mild and moderate/severe MAS as well as for late-onset respiratory distress. The risk of nonrespiratory comorbidities varied directly according to the severity of the respiratory distress. Late-onset respiratory distress shares several risk factors with MAS, as defined by Rossi et al. The two conditions may represent different manifestations of the same disease process.