Transient Tachypnea of the Newborn

Basics

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.

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.

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.

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