Transient Tachypnea of the Newborn
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- 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.
- Estimated 4 to 6 per 1,000 live births
- Incidence is likely underestimated.
- Most common cause of respiratory distress in newborns
- Higher in males
- Early gestation
- Cesarean section delivery (with or without preceding labor)
- Male gender
- Maternal diabetes
- 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.
- 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.
Transient pulmonary edema due to delayed clearance of fetal lung fluid
- 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.