A woman at 34-weeks gestation in her second pregnancy comes into spontaneous labour. Labour proceeds to a vaginal delivery of a male infant weighing 2100g. He has Apgar scores of 6 at one minute, 8 at five minutes. Over the next two to three hours he develops grunting respirations, tachypnoea (respiratory rate 60/min), and subcostal recession; and at four hours of age he requires 45% oxygen to maintain oxygenation. Which one of the following is the most likely cause of the infant’s respiratory distress?
The cause of respiratory difficulty in the neonatal period can usually be determined by a careful maternal history and a detailed account of the delivery details of the infant. Infants born prematurely with immature lungs will present with respiratory distress soon after birth despite good Apgar scores - requiring supplementary oxygen therapy, and the cause is usually due to a deficiency of lung surfactant and development of hyaline membrane lung disease. This is the most likely cause in this infant. The history does not indicate any fetal distress and his Apgar scores are good, hence birth asphyxia and meconium aspiration are highly unlikely causes for his clinical picture. While a tension pneumothorax may occur spontaneously and in association with hyaline membrane disease, it is usually associated with respiratory disease necessitating ventilatory support and presents as a rapid deterioration of the baby with increasing oxygen requirements.