Description

• Early onset of tachypnea (respiratory rate >60 breaths/minute) in the newborn following an uneventful delivery
• Symptoms of respiratory distress including mild retractions, expiratory grunting, and nasal flaring may occur. Cyanosis is rarely involved.

Epidemiology

• Estimated 4 to 6 per 1,000 live births
• Incidence is likely underestimated.
• Most common cause of respiratory distress in newborns
• Higher in males

Risk Factors

• Early gestation
• Cesarean section delivery (with or without preceding labor)
• Male gender
• Maternal diabetes
• Macrosomia
• Low birth weight
• Maternal history of asthma
• Unexplained transient tachypnea of the newborn (TTN) in individuals belonging to the same family suggests a genetic predisposition.

General Prevention

• Vaginal delivery should be recommended in the absence of maternal or fetal indications for cesarean section.
• Elective cesarean section before 39 weeks’ gestation should be avoided.

Pathophysiology

Transient pulmonary edema due to delayed clearance of fetal lung fluid

Etiology

• During fetal life, pulmonary epithelial cells are secretory, delivering chloride into the alveolar space.
• Sodium and water follow chloride into the alveoli, establishing and maintaining fetal lung fluid.
• During labor and delivery, fetal lung fluid is absorbed through a variety of proposed mechanisms:
  • Epithelial cells transition from secretory cells to absorptive cells in response to circulating epinephrine levels, which trigger opening of epithelial sodium channels (ENaC).
  • Compression of the fetal thorax from uterine contractions and passage through the vaginal canal contributes to removal of fluid from the lungs through the pulmonary circulation.
  • Prostaglandin-mediated dilation of lymphatic vessels occurs with resultant absorption of interstitial lung fluid into the lymphatic system.
• TTN occurs when there is inadequate fluid clearance from the lungs.
• It is believed that this excess interstitial lung fluid contributes to decreased lung compliance.