Preterm (Premature) Newborns

Several problems arise when an infant is born before the brain is fully developed. These problems include

• Inconsistent breathing: The part of the brain that controls regular breathing may be so immature that preterm newborns breathe inconsistently, with short pauses in breathing or periods during which breathing stops completely for 20 seconds or longer (apnea of prematurity).

• Difficulty coordinating feeding and breathing: The parts of the brain that control reflexes involving the mouth and throat are immature, so preterm newborns may not be able to suck and swallow normally, resulting in difficulty coordinating feeding with breathing.

• Bleeding (hemorrhage) in the brain: Newborns born very prematurely are at increased risk of bleeding in the brain.

• Delays in development of motor, intellectual, social, and emotional skills

An underdeveloped digestive tract and liver can cause several problems, including the following:

• Frequent episodes of spitting-up: Initially, preterm newborns may have difficulty with feedings. Not only do they have immature sucking and swallowing reflexes, but their small stomach empties slowly, which can lead to frequent episodes of spitting up (reflux).

• Frequent episodes of not tolerating feedings: The intestines of preterm newborns move very slowly, and preterm newborns frequently have difficulty passing stools. Because of the slow movement of the intestinal tract, preterm infants do not easily digest the breast milk or formula they are given.

• Intestinal damage: Very preterm newborns may develop a serious condition in which part of the intestine becomes severely damaged and may cause infection (called necrotizing enterocolitis).

• Hyperbilirubinemia: Preterm newborns are prone to developing hyperbilirubinemia. In hyperbilirubinemia, the newborn's liver is slow in clearing bilirubin (the yellow bile pigment that results from the normal breakdown of red blood cells) from the blood. Thus, the yellow pigment accumulates, giving the skin and the whites of the eyes a yellow color (jaundice). Preterm newborns tend to become jaundiced in the first few days after birth. Usually, jaundice is mild and resolves as newborns take in larger amounts during feedings and have more frequent bowel movements (bilirubin is removed in the stool, giving it its initial yellow color). Rarely, very high levels of bilirubin accumulate and put newborns at risk of developing kernicterus. Kernicterus is a form of brain damage caused by deposits of bilirubin in the brain.

Infants born very prematurely have low levels of antibodies, which are proteins in the blood that help protect against infection. Antibodies from the mother cross the placenta late in the pregnancy and help protect the newborn from infection at birth.

Preterm newborns have fewer of their mother's protective antibodies and therefore are at higher risk of developing infections, especially infection in the blood (sepsis in the newborn) or tissues around the brain (meningitis). The use of invasive devices for treatment after birth, such as catheters in blood vessels and breathing tubes (endotracheal tubes), further increases the risk of developing serious bacterial infections.

Before delivery, waste products produced in the fetus are removed by the placenta and then excreted by the mother’s kidneys. After delivery, the newborn’s kidneys must take over these functions. Kidney function is diminished in very preterm newborns but improves as the kidneys mature. Newborns with underdeveloped kidneys may have difficulty regulating the amount of salt and other electrolytes as well as water in the body.

Kidney problems may lead to growth failure and a buildup of acid in the blood (called metabolic acidosis).

The lungs of preterm newborns may not have had enough time to fully develop before birth. The tiny air sacs called alveoli that absorb oxygen from the air and remove carbon dioxide from the blood are not formed until about the beginning of the last third of pregnancy (third trimester). In addition to this structural development, the tissues of the lungs must make a fatty material called surfactant. Surfactant coats the inside of the air sacs and allows them to remain open throughout the breathing cycle, making it easy to breathe. Without surfactant, the air sacs tend to collapse at the end of each breath, making breathing very difficult. Usually, the lungs do not make surfactant until about 32 weeks of pregnancy, and production is typically not adequate until about 34 to 36 weeks.

These factors mean that babies born early are at risk of breathing problems, including respiratory distress syndrome (RDS). Newborns with breathing problems may need help with breathing with a ventilator (a machine that helps air get in and out of the lungs). The more preterm the newborn, the less surfactant is available, and the greater the likelihood that respiratory distress syndrome will develop.

There is no treatment to make the lung structure mature more rapidly, but with adequate nutrition, the lungs continue to mature over time.

There are two approaches to increase the amount of surfactant and reduce the likelihood and severity of respiratory distress:

• After birth: Doctors may give surfactant directly into the newborn's windpipe (trachea).

Bronchopulmonary dysplasia (BPD) is a chronic lung disorder that can occur in preterm newborns, particularly the least mature infants. Most infants who have BPD have had respiratory distress syndrome and needed treatment with a ventilator. In BPD, the lungs develop scar tissue and the infant needs continued help with breathing, sometimes with a ventilator. In most cases, the infant very slowly recovers from the disease.

Infants who are born prematurely are at increased risk of becoming seriously ill if they are infected with respiratory syncytial virusnirsevimabPrevention of RSV).

The retina is the light-sensitive tissue at the back of the eye. The retina is nourished by blood vessels on its surface. The blood vessels grow from the center of the retina to the edges during the course of the pregnancy and do not finish growing until near term.

In preterm infants, particularly the least mature infants, the blood vessels may stop growing and/or grow abnormally. Many preterm infants need extra oxygen, and this also can cause the blood vessels of the retina to grow abnormally. The abnormal vessels can bleed or cause scar tissue that can pull on the retina. This disorder is called retinopathy of prematurity and it occurs after birth. In the most severe cases, the retina detaches from the back of the eye and causes blindness.

Preterm newborns are also at increased risk of developing other eye problems, such as nearsightedness (myopia), misalignment of the eyes (strabismus), or both.

Because preterm newborns have difficulty feeding and maintaining normal blood sugar (glucose) levels, they are often treated with glucose solutions given by vein (intravenously) or given small, frequent feedings. Without regular feedings, preterm newborns may develop low blood sugar levels (hypoglycemia). Most newborns with hypoglycemia do not develop symptoms. Other newborns become listless with poor muscle tone, feed poorly, or become jittery. Rarely, seizures develop.

Preterm newborns are also prone to developing high blood sugar levels (hyperglycemia

Preterm newborns, particularly extremely preterm infants, may develop metabolic bone disease. Metabolic bone disease is a reduction in the minerals in bone. A preterm newborn may have inadequate mineral reserves because most calcium and phosphorus reserves are acquired between 25 and 40 weeks of gestation.

Some preterm newborns do not produce enough thyroid hormone (have hypothyroidism) because of their prematurity. Sometimes, it is difficult to differentiate the temporary hypothyroidism in a preterm newborn from permanent congenital hypothyroidism, which usually results from a defect in thyroid gland development. Preterm newborns sometimes need to be treated with thyroid hormone for some period of time. At first, newborns may have no symptoms. Later, if hypothyroidism remains undiagnosed or untreated, various symptoms develop. The newborn may become sluggish (lethargic) and have a poor appetite, yellowing of the skin (jaundice), low muscle tone, constipation, and a low heart rate. Eventually, if still untreated, the infant may develop dry, cool, mottled skin, coarse facial features (such as a flat, broad nasal bridge and a puffy face), coarse hair, abdominal swelling, low blood pressure, a low number of red blood cells (anemia), and an enlarged tongue.

A common issue among preterm infants is a patent ductus arteriosus (PDA). The ductus arteriosus is a blood vessel in the fetus that connects the two large arteries leaving the heart, the pulmonary artery and the aorta (see Normal Fetal Circulation). In a full-term infant, the muscle wall of the ductus arteriosis closes the blood vessel in the first few hours or days of life. In preterm infants, however, the blood vessel may stay open, resulting in excessive blood flow through the lungs and requiring more work from the heart.

In most preterm infants, the PDA eventually closes on its own, but medications are sometimes given to help the PDA close more quickly. In some cases, a surgical procedure to close the PDA is done.

Body temperature is maintained by the brain. Because preterm newborns do not have a mature brain, they have trouble regulating their body temperature.

Preterm newborns have a large skin surface area relative to their weight compared to full-term newborns, so they tend to lose heat rapidly and have difficulty maintaining normal body temperature, especially if they are in a cool room, there is a draft, or they are near a window when it is cold outside. If the baby is not kept warm, the body temperature falls (called hypothermia). Newborns who have hypothermia gain weight poorly and may have a number of other complications. To prevent hypothermia, preterm babies are kept warm in an incubator or with an overhead radiant warmer (see Neonatal intensive care unit [NICU]).

Very preterm newborns may need to be hospitalized in a neonatal intensive care unit for days, weeks, or months. They may require a breathing tube and a machine that helps air get in and out of the lungs (ventilator) until they are able to breathe on their own.

They receive nutrition into their veins until they can tolerate feedings into their stomach through a feeding tube and eventually feedings by mouth. The mother’s breast milk is the best food for preterm infants. Use of breast milk decreases the risk of developing an intestinal problem called necrotizing enterocolitis and infections. Because breast milk is low in some nutrients like calcium, it may need to be mixed with a fortifying solution for newborns who have a very low birthweight. Infant formulas made specifically for preterm infants that are high in calories also can be used when necessary.

To keep warm, these newborns need to be kept in an incubator until they are able to maintain a normal body temperature.

Extremely preterm newborns require all the same care as very preterm newborns. Like very preterm newborns, these newborns cannot be released from the hospital until they are able to breathe on their own, take oral feedings, maintain a normal body temperature, and gain weight.

Preterm infants typically remain hospitalized until their medical problems are under satisfactory control and they are

• Taking an adequate amount of breast milk, formula, or both without special assistance

• Gaining weight steadily

• Able to maintain a normal body temperature in a crib

• No longer having pauses in breathing (apnea of prematurity) or a slow heart rate that requires treatment

Most preterm infants are ready to go home when they are at 35 to 37 weeks of gestational age and weigh 4 to 5 pounds (2 to 2.5 kilograms). However, there is wide variation. The length of time the infant stays in the hospital does not affect the long-term prognosis.

Because preterm newborns are at risk of stopping breathing (apnea) and of having low levels of oxygen in the blood and a slow heart rate while in a car seat, many hospitals in the United States do a car seat challenge test before preterm babies are discharged. The test is done to determine whether babies are stable in the semi-reclined position of a car seat. This test is usually done using the car seat provided by the parents. Preterm babies, including those who pass the test, should be observed by a non-driving adult during all car seat travel until the babies have reached the due date and have remained consistently able to tolerate being in the car seat. Because the baby's color should be observed, travel should be limited to daylight hours. Long trips should be broken up into 45- to 60-minute segments so that the baby can be taken out of the car seat and repositioned.

Surveys show that most car seats are not installed optimally, so a check of the car seat by a certified car seat inspector is recommended. Inspection sites in the United States can be found through the National Highway Traffic Safety Administration. Some hospitals offer an inspection service. Car seat installation advice should be given only by a certified car seat expert.

The American Academy of Pediatrics recommends that car seats be used only for vehicular transportation and not as an infant seat or bed at home. Many doctors also recommend that parents do not put preterm infants in swings or bouncy seats for the first few months at home.

After discharge, preterm infants are carefully monitored for developmental problems and receive physical, occupational, and speech and language therapy as needed.