[Clinical features of respiratory diseases in late preterm neonates]

To evaluate the clinical features of respiratory diseases of late preterm neonates.

Six hundred and thirty late preterm infant(gestational age: 34~36+6weeks),4401 cases of term infants and 328 early preterm infants who were born at the obstetrical department of Peking University 3rd Hospital from January 2009 to December 2010 were enrolled. Among them 84 late preterm infants, 135 term infants and 182 early preterm infants developed respiratory diseases. The incidence of respiratory diseases,clinical features and the severity of the diseases were compared among the three groups.

The incidence and mortality rates of respiratory diseases and the percentage of severe cases were significantly higher in the late preterm group than in the term group, but lower than in the early preterm group (P<0.01). The symptoms of respiratory disease occurred earlier in the late preterm group than in the term group, but later than in the early preterm group (P<0.01). The late preterm group had a significantly higher incidence of tachypnea and lower incidence of retraction sign when compared with the term and early preterm groups (P<0.05). The percentages requiring oxygen therapy and mechanical ventilation in the late preterm group were both significantly higher than in the term group, but lower than in the early preterm group (P<0.05). The multiple linear regression analysis showed 11 factors associated with the severity of respiratory diseases: decreased arterial partial pressure of oxygen, hematokrit, pH value and respiratory rate, arterial oxyhemoglobin saturation, systolic arterial pressure, 5 minute Apgar score and gestational age, and increased blood urea nitrogen, heart rate and respiratory rate.

Late preterm infants are more likely to develop respiratory diseases than term infants, and to develop a more severe condition and need a more intensive respiratory support treatment. Tachypnea is a common presentation of dyspnea in late preterm infants and occurs earlier than in term infants but later than in early preterm infants. It may usually indicate a serious condition when dyspnea, abnormal heart rate and blood pressure, and multisystem damages occur in late preterm infants.