Maternal diabetes mellitus: leads to ↑ fetal insulin, which inhibits surfactant synthesis
Hereditary
Cesarean delivery: results in lower levels of fetal glucocorticoids than vaginal delivery, in which higher levels are released as a response to stress from uterine contractions
Hydrops fetalis
Multifetal pregnancies
Male sex
Pathophysiology
Surfactant deficiency
Little or no reduction of alveolar surface tension → increased alveolar collapse → atelectasis → decreased lung compliance and functional residual capacity → hypoxemia and hypercapnia
Clinical features
Maternal history of premature birth
Onset of symptoms: usually immediately after birth but can occur up to 72 hours postpartum
Signs of increased respiratory effort
Tachypnea
Nasal flaring and moderate to severe subcostal/intercostal and jugular retractions
Characteristic expiratory grunting
Decreased breath sounds on auscultation
Cyanosis due to pulmonary hypoxic vasoconstriction
Diagnostics
X-ray chest
Interstitial pulmonary edema with perihilar streaking
Diffuse, fine, reticulogranular (ground-glass) densities with low lung volumes and air bronchograms
Atelectasis
Amniocentesis for prenatal testing of NRDS: screening for markers of fetal lung immaturity
Lecithin-sphingomyelin ratio < 1.5 (≥ 2 is considered mature)
The amount of sphingomyelin in the amniotic fluid remains relatively consistent during pregnancy.
The amount of lecithin, which is the major component of surfactant, starts increasing after week 26 of gestation.
The lower the lecithin-sphingomyelin ratio, the more likely it is that the lungs are immature.
Complications
Bronchopulmonary dysplasia (BPD)
Definition: chronic lung condition secondary to prolonged mechanical ventilation and oxygen therapy for NRDS
Etiology: Pulmonary barotrauma and oxygen toxicity with subsequent inflammation of lung tissue due to ventilation of the immature lung (ventilation for more than 28 days)
Clinical features
Seen in infants < 32 weeks
Persistence of symptoms similar to NRDS (e.g., tachypnea, grunting, nasal flaring)
Episodes of desaturation
Diagnostics
X-ray chest: diffuse, fine, granular densities, areas of atelectasis interspersed with areas of hyperinflation
Blood gas analysis: respiratory and metabolic acidosis
Histology: atelectasis, fibrosis, emphysematous alveolar changes (decreased number and septation of alveoli)
