About 1% of all newborns develop TTN, which usually eases after a few days with treatment. Babies born with TTN need special monitoring and treatment while in the hospital, but afterwards most make a full recovery, with no lasting effect on growth and development.
About Transient Tachypnea of the Newborn
Before birth, a fetus' lungs are filled with fluid. While inside the mother, a fetus does not use the lungs to breathe — all oxygen comes from the blood vessels of the placenta.
As the due date nears, the baby's lungs begin to clear the fluid in response to hormonal changes. Some fluid may also be squeezed out during the birth, as a baby passes through the birth canal. After the birth, as a newborn takes those first breaths, the lungs fill with air and more fluid is pushed out of the lungs. Any remaining fluid is then coughed out or gradually absorbed into the body through the bloodstream.
In infants with TTN, however, extra fluid in the lungs remains or the fluid is cleared too slowly. So it is more difficult for the baby to inhale oxygen properly, and the baby breathes faster and harder to get enough oxygen in.
Causes of TTN
TTN, also called "wet lungs" or type II respiratory distress syndrome, usually can be diagnosed in the hours after birth. It's not possible to detect before the birth whether a child will have it.
TTN can occur in both preemies (because their lungs are not yet fully developed) and full-term babies.
Newborns at higher risk for TTN include those who are:
- delivered by cesarean section (C-section)
- born to mothers with diabetes
- born to mothers with asthma
- small for gestational age (small at birth)
During vaginal births, especially with full-term babies, the pressure of passing through the birth canal squeezes some of the fluid out of the lungs. Hormonal changes during labor may also lead to absorption of some of the fluid. Babies who are small or premature or who are delivered via rapid vaginal deliveries or C-section don't undergo the usual squeezing and hormone changes of a vaginal birth. So they tend to have more fluid than normal in their lungs when they take their first breaths.
Signs and Symptoms of TTN
- rapid, labored breathing (tachypnea) of more than 60 breaths a minute
- grunting or moaning sounds when the baby exhales
- flaring nostrils or head bobbing
- retractions (when the skin pulls in between the ribs or under the ribcage during rapid or labored breathing)
- cyanosis (when the skin turns a bluish color) around the mouth and nose
- Other than the above symptoms, infants with TTN will look fairly healthy.
Because TTN has symptoms that are initially similar to more severe newborn respiratory problems (such as pneumonia or persistent pulmonary hypertension), doctors may use chest X-rays in addition to physical examination to make a diagnosis.
Other indicators used to make a diagnosis of TTN:
- If an infant has TTN, the X-ray picture of the lungs will appear streaked and fluid may be seen. The X-ray will otherwise appear fairly normal.
- Pulse-oximetry monitoring, which is when a small piece of tape containing an oxygen sensor is placed around a baby's foot or hand and connected to a monitor. This tells doctors how well the lungs are sending oxygen to the blood and is also useful in monitoring TTN.
- Sometimes oxygen levels need to be checked with a blood test.
- A complete blood count (CBC) may also be drawn from one of the baby's veins or a heel to check for signs of infection.
As with any newborn who has a breathing problem, infants with TTN are closely watched. Monitors will measure heart rate, breathing rate, and oxygen levels. Some are simply monitored to ensure that their breathing rates slow down and their oxygen levels remain normal. Others might need to receive extra oxygen through a mask, a small tube under the nose, or under a plastic oxygen hood (sometimes called a "oxyhood").
If a baby is still struggling to breathe, even when oxygen is given, continuous positive airway pressure (CPAP) might be used to keep air flowing through the lungs. With CPAP, a baby wears special oxygen prongs(a type of tubing placed directly into the nose) and a machine continuously pushes a stream of pressurized air into the baby's nose to help keep the lungs open during breathing.
In the most severe cases of TTN, a baby would need ventilator support, but this is rare.
Nutrition can be a problem if an infant is breathing so fast that he or she can't suck, swallow, and breathe simultaneously. In that case, intravenous (IV) fluids provide hydration and will prevent the infant's blood sugar from dipping to dangerously low levels.
Within 24 to 48 hours, the breathing of infants with TTN usually improves and returns to normal, and within 72 hours, all symptoms of TTN end.
If fluid stays in a baby's lungs beyond that, or if an infant is not improving, doctors will look for other medical problems.