Preterm Infants

ByArcangela Lattari Balest, MD, University of Pittsburgh, School of Medicine
Reviewed/Revised Nov 2023
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An infant born before 37 weeks of gestation is considered preterm.

In 2021 in the United States, 10.48% of births were preterm (1), and in 2018, 26.53% of births were early term (significantly increased from 26% in 2017) (2). Preterm infants, even late preterm infants who are the size of some full-term infants, have increased morbidity and mortality compared to full-term infants because of their prematurity.

Prematurity is defined by the gestational age at birth.

Previously, any infant weighing < 2.5 kg was considered preterm. Although preterm infants tend to be small, this weight-based definition is often incorrect because many infants weighing < 2.5 kg are term or postterm but are small for gestational age.

Gestational age

Gestational age is defined as the number of weeks between the first day of the mother's last normal menstrual period and the day of delivery. More accurately, the gestational age is the difference between 14 days before the date of conception and the date of delivery. Gestational age is not the actual embryologic age of the fetus, but it is the universal standard among obstetricians and neonatologists for discussing fetal maturation.

Birth prior to 37 weeks of gestation is considered preterm. Preterm infants are further categorized as (3)

Birthweight

Preterm infants tend to be smaller than term infants. The Fenton growth charts provide a more precise assessment of growth vs gestational age (see figures Fenton Growth Chart for Preterm Boys and Fenton Growth Chart for Preterm Girls).

Preterm infants are categorized by birthweight:

  • < 1000 g: Extremely low birthweight (ELBW)

  • 1000 to 1499 g: Very low birthweight (VLBW)

  • 1500 to 2500 g: Low birthweight (LBW)

General references

  1. 1. Hamilton BE, Martin JA, Osterman MJ: Births: Provisional Data for 2021. National Center for Health Statistics. National Vital Statistics System, Vital Statistics Rapid Release Program, no 20. Hyattsville, MD. National Center for Health Statistics. 2022.

  2. 2. Martin JA, Hamilton BE, Osterman MJ: Births in the United States, 2018. NCHS Data Brief, no 346. Hyattsville, MD. National Center for Health Statistics. 2019.

  3. 3. Howson CP, Kinney MV, Lawn JE, editorBorn Too Soon: The Global Action Report on Preterm Birth. New York, March of Dimes, PMNCH, Save the Children, World Health Organization, 2012.

Etiology of Prematurity

Preterm delivery may be

  • Indicated because of obstetric risks or complications

  • Spontaneous because of preterm labor

Obstetric risks or complications

The American College of Obstetricians and Gynecologists (ACOG) recommends late preterm delivery in conditions such as multiple gestation with complications, preeclampsia, placenta previa/placenta accreta, and prelabor rupture of membranes (1).

ACOG recommends delivery as early as 32 weeks in selected cases involving multiple gestation with complications. Quasi-elective delivery earlier than 32 weeks is done on a case-by-case basis to manage severe maternal and/or fetal complications.

Spontaneous preterm delivery

In an individual patient, spontaneous preterm delivery may or may not have an obvious immediate trigger (eg, infection [see Intra–Amniotic Infection and Infectious Disease in Pregnancy], placental abruption). There are many risk factors (2):

Past obstetric or gynecologic history:

Obstetric risk factors related to the current pregnancy:

Multiple gestation is an important risk factor; 59% of twins and > 98% of higher-order multiples are delivered prematurely. Many of these infants are very preterm; 10.7% of twins, 37% of triplets, and > 80% of higher-order multiples are delivered at < 32 weeks of gestation (4).

Lifestyle or demographic risk factors:

  • Younger or older maternal age (eg, < 16 years, > 35 years)

  • Non-Hispanic Black or American Indian/Alaska Native women (in the United States)

  • Undernutrition

  • Cigarette smoking

  • Use of alcohol or illicit drugs

  • Exposure to certain environmental pollutants

  • Domestic violence

  • Stress or lack of social support

  • Long work hours with long periods of standing

It is unclear how much risk some of these lifestyle or demographic risk factors contribute independent of their effect on other risk factors (eg, nutrition, access to medical care).

Etiology references

  1. 1. American College of Obstetricians and Gynecologists’ Committee on Obstetric Practice, Society for Maternal-Fetal Medicine: Medically Indicated Late-Preterm and Early-Term Deliveries: ACOG Committee Opinion, Number 831. Obstet Gynecol 138(1):e35-e39, 2021. doi: 10.1097/AOG.0000000000004447

  2. 2. National Institute of Child Health and Human Development: What are the risk factors for preterm labor and birth? Accessed October 6, 2023.

  3. 3. Saccone G, Perriera L, Berghella V: Prior uterine evacuation of pregnancy as independent risk factor for preterm birth: A systematic review and metaanalysis. Am J Obstet Gynecol 214(5):572-591, 2016. doi: 10.1016/j.ajog.2015.12.044

  4. 4. Hamilton BE, Martin JA, Osterman MJ: Births: Provisional Data for 2021. National Center for Health Statistics. National Vital Statistics System, Vital Statistics Rapid Release Program, no 20. Hyattsville, MD. National Center for Health Statistics. 2022.

Complications of Prematurity

The incidence and severity of complications of prematurity increase with decreasing gestational age and birthweight. Some complications (eg, necrotizing enterocolitis, retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage) are uncommon in late preterm infants.

Most complications relate to dysfunction of immature organ systems. In some cases, complications resolve completely; in others, there is residual organ dysfunction.

Central nervous system (CNS)

CNS complications include

Infants born before 34 weeks of gestation have inadequate coordination of sucking and swallowing reflexes and need to be fed intravenously or by gavage. When to begin oral feedings is based on the infant's display of readiness cues for feeding, physiologic stability, and lack of need for advanced respiratory support (eg, ventilator, high-flow nasal catheters, CPAP). Evaluation for signs of feeding readiness does not begin until after 32 weeks postmenstrual age.

Immaturity of the respiratory center in the brain stem results in apneic spells (central apnea). Apnea may also result from hypopharyngeal obstruction alone (obstructive apnea). Both may be present (mixed apnea).

The periventricular germinal matrix (a highly cellular mass of embryonic cells that lies over the caudate nucleus on the lateral wall of the lateral ventricles of a fetus) is prone to hemorrhage, which may extend into the cerebral ventricles (intraventricular hemorrhage). Infarction of the periventricular white matter (periventricular leukomalacia) may also occur for reasons that are incompletely understood. Hypotension, inadequate or unstable brain perfusion, and blood pressure peaks (as when fluid or colloid is given rapidly IV) may contribute to cerebral infarction or hemorrhage. Periventricular white matter injury is a major risk factor for cerebral palsy and neurodevelopmental delays.

Preterm infants, particularly those with a history of sepsis, necrotizing enterocolitis, hypoxia, and intraventricular and/or periventricular hemorrhages or leukomalacia, are at risk of developmental and cognitive delays (see also Childhood Development). These infants require careful follow-up during the first year of life to identify auditory, visual, and neurodevelopmental delays. Careful attention must be paid to developmental milestones, muscle tone, language skills, and growth (weight, length, and head circumference). Infants with identified delays in visual skills should be referred to a pediatric ophthalmologist. Infants with auditory and neurodevelopmental delays (including increased muscle tone and abnormal protective reflexes) should be referred to early intervention programs that provide physical, occupational, and speech therapy. Infants with severe neurodevelopmental problems may need to be referred to a pediatric neurologist or neurodevelopmental pediatrician.

Ocular

Ocular complications include

Retinal vascularization is not complete until near term. Preterm delivery and the therapies needed to treat it (eg, supplemental oxygen) may interfere with the normal vascularization process, resulting in abnormal vessel development and sometimes defects in vision including blindness. Incidence of ROP is inversely proportional to gestational age. Disease usually manifests between 32 weeks and 34 weeks of gestational age.

Incidence of myopia and strabismus increases independently of ROP.

Infectious

Infectious complications include

Sepsis or meningitis is about 4 times more likely in the preterm infant, occurring in almost 25% of very low-birthweight infants. The increased likelihood results from indwelling intravascular catheters and endotracheal tubes, areas of skin breakdown, and markedly reduced serum immunoglobulin levels (see Neonatal Immunologic Function).

Pulmonary

Pulmonary complications include

Surfactant production is often inadequate to prevent alveolar collapse and atelectasis, which result in respiratory distress syndrome (hyaline membrane disease). Many other factors can contribute to respiratory distress in the first week of life. Regardless of the cause, many extremely preterm and very preterm infants have persistent respiratory distress and an ongoing need for respiratory support. Some infants are successfully weaned off support over a few weeks; others develop chronic lung disease (bronchopulmonary dysplasia) with need for prolonged respiratory support using a high-flow nasal cannula, continuous positive airway pressure (CPAP) or other noninvasive ventilatory assistance, or mechanical ventilation. Respiratory support may be given with room air or with supplemental oxygen. If supplemental oxygen is required, the lowest oxygen concentration that can maintain target oxygen saturation levels of 90 to 95% should be used (see table Neonatal Oxygen Saturation Targets).

respiratory syncytial virus (RSV)nirsevimab is not available.

In addition, the American College of Obstetricians and Gynecologists recommends maternal RSV vaccination between 32 and 36 6/7 weeks of gestation, if birth is expected during the RSV season, to prevent RSV lower respiratory tract infection in infants (1). However, it is uncertain whether maternal RSV vaccination will benefit many preterm infants because timing of birth may not allow timely administration of the vaccine.

Gastrointestinal

Gastrointestinal complications include

  • Feeding intolerance, with increased risk of aspiration

  • Necrotizing enterocolitis

Feeding intolerance is extremely common because preterm infants have a small stomach, immature sucking and swallowing reflexes, and inadequate gastric and intestinal motility. These factors hinder the ability to tolerate both oral and nasogastric feedings and create a risk of aspiration. Feeding tolerance usually increases over time.

Necrotizing enterocolitis usually manifests with bloody stool, feeding intolerance, and a distended, tender abdomen. Necrotizing enterocolitis is the most common surgical emergency in the preterm infant. Complications of neonatal necrotizing enterocolitis include bowel perforation with pneumoperitoneum, intra-abdominal abscess formation, stricture formation, short bowel syndrome, septicemia, and death.

Cardiac

The overall incidence of structural congenital heart defects among preterm infants is low. The most common cardiac complication is

The ductus arteriosus is more likely to fail to close after birth in preterm infants. The incidence of PDA increases with increasing prematurity; PDA occurs in almost half of infants whose birthweight is < 1750 g and in about 80% of those < 1000 g. About one third to one half of infants with PDA have some degree of heart failure. Preterm infants 29 weeks of gestation at birth who have respiratory distress syndrome have a 65 to 88% risk of a symptomatic PDA. If infants are ≥ 30 weeks of gestation at birth, the ductus closes spontaneously in 98% by the time of hospital discharge.

Renal

Renal complications include

Renal function is limited, so the concentrating and diluting limits of urine are decreased.

Late metabolic acidosis and growth failure may result from the immature kidneys’ inability to excrete fixed acids, which accumulate with high-protein formula feedings and as a result of bone growth. Sodium and bicarbonate are lost in the urine.

Metabolic

Metabolic complications include

  • Hypoglycemia and hyperglycemia

  • Hyperbilirubinemia

  • Metabolic bone disease (osteopenia of prematurity)

  • Congenital hypothyroidism

Neonatal hypoglycemia and neonatal hyperglycemia are discussed elsewhere.

Hyperbilirubinemia occurs more commonly in the preterm as compared to the term infant, and kernicterus (brain damage caused by hyperbilirubinemia) may occur at serum bilirubin levels as low as 10 mg/dL (170 micromol/L) in small, sick, preterm infants. The higher bilirubin levels may be partially due to hepatic excretion mechanisms that are inadequately developed for extrauterine life, including deficiencies in the uptake of bilirubin from the serum, its hepatic conjugation to bilirubin diglucuronide, and its excretion into the biliary tree. Decreased intestinal motility enables more bilirubin diglucuronide to be deconjugated within the intestinal lumen by the luminal enzyme beta-glucuronidase, thus permitting increased reabsorption of unconjugated bilirubin (enterohepatic circulation of bilirubin). Conversely, early feedings increase intestinal motility and reduce bilirubin reabsorption and can thereby significantly decrease the incidence and severity of physiologic jaundice. Uncommonly, delayed clamping of the umbilical cord (which has several benefits and is generally recommended) may increase the risk of hyperbilirubinemia by allowing the transfusion of RBCs thus increasing RBC breakdown and bilirubin production.

Metabolic bone disease with osteopenia is common, particularly in extremely preterm infants. It is caused by inadequate intake of calcium, phosphorus, and vitamin D

Congenital hypothyroidism, characterized by low thyroxine (T4) and elevated thyroid-stimulating hormone (TSH) levels, is much more common among preterm infants than full-term infants. In infants with a birthweight of < 1500 g, the rise in TSH may be delayed for several weeks, necessitating repeated screening for detection. Transient hypothyroxinemia, characterized by low T4 and normal TSH levels, is very common among extremely preterm infants; treatment with L-thyroxine is not beneficial (2).

Temperature regulation

The most common temperature regulation complication is

Preterm infants have an exceptionally large body surface area to volume ratio. Therefore, when exposed to temperatures below the neutral thermal environment, they rapidly lose heat and have difficulty maintaining body temperature. The neutral thermal environment is the environmental temperature at which metabolic demands (and thus calorie expenditure) to maintain normal body temperature (36.5 to 37.5° C rectal) are lowest.

Complications references

  1. 1. American College of Obstetricians and Gynecologists: Practice Advisory: Maternal Respiratory Syncytial Virus Vaccination. 2023. Accessed October 6, 2023.

  2. 2. Wassner AJ, Brown RS: Hypothyroidism in the newborn period. Curr Opin Endocrinol Diabetes Obes 20(5):449–454, 2013. doi: 10.1097/01.med.0000433063.78799.c2

Diagnosis of Prematurity

  • Obstetric history and postnatal physical parameters

  • Fetal ultrasonography

  • Screening tests for complications

A diagnosis of prematurity depends on the best estimate of gestational age. Neonatal gestational age is usually defined by counting the number of weeks between the first day of the mother's last normal menstrual period and the date of delivery. However, determining gestational age based on the last menstrual period may be inaccurate if a pregnant patient has irregular menses. Alternatively, sometimes the approximate or exact date of conception is known if ovulation tests or assisted reproductive technologies were used. Also, based on the first fetal ultrasound in a pregnancy, the estimated gestational age may be changed if the ultrasonographic results differ sufficiently from the menstrual dating. After delivery, newborn physical examination findings also allow clinicians to estimate gestational age, which can be confirmed by the new Ballard score.

Along with appropriate testing for any identified problems or disorders, routine evaluations include pulse oximetry, complete blood count, electrolytes, bilirubin level, blood culture, serum calcium, alkaline phosphatase, and phosphorus levels (to screen for osteopenia of prematurity), hearing evaluation, cranial ultrasonography (to screen for intraventricular hemorrhage and periventricular leukomalacia), and screening by an ophthalmologist for retinopathy of prematurity (depending on gestational age). Weight should be obtained and plotted on a growth chart every day. Length and head circumference should be plotted on an appropriate growth chart at weekly intervals. Head circumference should be obtained more often, sometimes daily, if hydrocephalus is a concern.

As with older neonates, routine newborn screening tests are done at 24 to 48 hours of age. Unlike full-term infants, preterm infants, especially extremely preterm infants, have a high rate of false-positive results (1). Mild elevations of several amino acids and abnormal acylcarnitine profiles are common and slight elevations of 17-hydroxyprogesterone levels and low thyroxine (T4) levels (typically with normal thyroid-stimulating hormone levels) are often present. Extremely preterm infants and very preterm infants are at risk of a delayed presentation of congenital hypothyroidism and should be periodically screened.

X-rays, often obtained for other reasons, may provide evidence of osteopenia and/or unsuspected fractures. DXA scanning and quantitative ultrasonography scanning may detect osteopenia but are not in widespread use.

Diagnosis reference

  1. 1. Clark RH, Kelleher AS, Chace DH, Spitzer AR: Gestational age and age at sampling influence metabolic profiles in premature infants. Pediatrics 134(1):e37–e46, 2014. doi: 10.1542/peds.2014-0329

Preterm, Very Preterm, and Extremely Preterm Infants

A preterm infant is an infant born before 37 weeks of gestation. Very preterm infants are 28 to 31 6/7 weeks. Extremely preterm infants are < 28 weeks.

Complications

The incidence and severity of complications of preterm infants increase with decreasing gestational age and birthweight. Some complications (eg, necrotizing enterocolitis, retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage) occur primarily in infants delivered at < 34 weeks.

Symptoms and Signs

The preterm infant is small, usually weighing < 2.5 kg, and tends to have thin, shiny, pink skin through which the underlying veins are easily seen. Little subcutaneous fat, hair, or external ear cartilage exists. Spontaneous activity and tone are reduced, and extremities are not held in the flexed position typical of term infants.

In males, the scrotum may have few rugae, and the testes may be undescended. In females, the labia majora do not yet cover the labia minora.

Reflexes develop at different times during gestation. The Moro reflex begins by 28 to 32 weeks of gestation and is well established by 37 weeks. The palmar reflex starts at 28 weeks and is well established by 32 weeks. The tonic neck reflex starts at 35 weeks and is most prominent at 1 month postterm.

Evaluation

  • Monitoring in a neonatal intensive care unit (NICU)

  • Screening for complications

NICU monitoring and screening

Serial physical examinations are important in monitoring infants' progress and detecting new problems (eg, respiratory problems, jaundice). Frequent weight assessments are necessary to optimize weight-based medication dosages and feeding.

  • Growth and nutrition: Weight should be monitored closely, particularly in the first days of life when there is a contraction of the extracellular volume; dehydration with severe hypernatremia may develop. Weight should be assessed daily if tolerated; length and head circumference should be assessed weekly and plotted on an appropriate growth chart.

  • Electrolyte balance: Serum electrolytes, glucose, calcium, and phosphate levels need to be periodically measured, particularly in infants receiving parenteral fluids and/or nutrition (eg, very preterm and extremely preterm infants), and during the diuresis seen in the first days of life (see also Metabolic, Electrolyte, and Toxic Disorders in Neonates).

  • Respiratory status: Pulse oximetry and sometimes transcutaneous or end-tidal PCO2 are monitored continually; arterial or capillary blood gas tests are done as needed (see also Respiratory Problems in Neonates).

  • Apnea and bradycardia: External cardiorespiratory monitoring is usually continued until close to the time of discharge.

  • Hematologic abnormalities: Complete blood count (CBC), reticulocyte count, and differential count are done initially and at intervals to detect common abnormalities (see also Perinatal Hematologic Disorders).

  • Hyperbilirubinemia: Transcutaneous and/or serum bilirubin levels are measured to detect and monitor this disorder.

  • Systemic infection: CBC with manual differential, C-reactive protein, blood culture, and sometimes procalcitonin levels are often done to facilitate early detection of neonatal sepsis.

  • Central nervous system infection: Lumbar puncture is typically reserved for infants with clear signs of infection and/or seizures, a positive blood culture, or an infection that is not responding to antibiotics.

  • Intraventricular hemorrhage (IVH): Screening cranial ultrasonography is indicated at 7 to 10 days in preterm infants < 32 weeks and in older preterm infants with complex courses (eg, known IVH, cardiorespiratory and/or metabolic instability).

Intraventricular hemorrhage in extremely preterm infants may be clinically silent, and a routine cranial ultrasound is recommended for these infants. The incidence of IVH decreases with increasing gestational age, so routine screening of preterm infants > 32 weeks is not considered useful unless they had significant complications. Most IVHs occur in the first week of life and, unless there are clinical indications of hemorrhage, the highest yield is obtained by scanning at 7 to 10 days of age. Extremely preterm infants are at risk of periventricular leukomalacia, which may develop later in the course (with or without hemorrhage), so they should have cranial ultrasonography at 6 weeks of age. Infants with moderate or severe hemorrhages should be followed using head circumference measurements and periodic cranial ultrasonography to detect and monitor hydrocephalus; there is no benefit in repeat scanning of infants with minor hemorrhage without clinical indication (1). However, close neurodevelopmental follow-up is recommended for infants who have any hemorrhage.

Later screening

Screening for retinopathy of prematurity is recommended for infants born ≤ 1500 g or ≤ 30 weeks of gestational age and for larger and more mature infants who have had an unstable clinical course. The first examination is done according to a schedule based on the infant's gestational age (see table Screening for Retinopathy of Prematurity). Examinations are usually repeated at 1- to 3-week intervals depending on the initial findings and are continued until the retina is mature. Some of these follow-up examinations are done after the infant is discharged. The use of digital photographic retinal images is an alternate method of examination and follow-up in areas where a skilled examiner is not routinely available.

Table

Evaluation reference

  1. 1. Kaeppler C, Switchenko N, DiGeronimo R, Yoder BA: Do normal head ultrasounds need repeating in infants less than 30 weeks gestation? J Matern Fetal Neonatal Med 29(15):2428-2433, 2016. doi: 10.3109/14767058.2015.1086741

Treatment of Preterm Infants

  • Supportive care

Specific disorders are treated as discussed elsewhere in THE MANUAL.

General supportive care of the preterm infant is best provided in a NICU or special care nursery and involves careful attention to the thermal environment, using servo-controlled incubators. Scrupulous adherence is paid to handwashing before and after all patient contact. Infants are continually monitored for apnea, bradycardia, and hypoxemia until 35 weeks of gestation.

Parents should be encouraged to visit and interact with the infant as much as possible within the constraints of the infant’s medical condition. Skin-to-skin contact between the infant and parent (kangaroo care) is beneficial for infant health and facilitates parental bonding. It is feasible and safe even when infants are supported by ventilators and infusions.

Feeding

Feeding should be by nasogastric tube until coordination of sucking, swallowing, and breathing is established at about 34 weeks of gestation, at which time breastfeeding is strongly encouraged. Most preterm infants tolerate breast milk, which provides immunologic and nutritional factors that are absent in cow’s milk formulas. However, breast milk does not provide sufficient calcium, phosphorus, and protein for very low-birthweight infants (ie, < 1500 g), for whom it should be mixed with a breast milk fortifier. Alternatively, specific preterm infant formulas that contain 20 to 24 kcal/oz (2.8 to 3.3 joules/mL) can be used.

In the initial 1 or 2 days, if adequate fluids and calories cannot be given by mouth or nasogastric tube because of the infant’s condition, IV parenteral nutrition with protein, glucose, and fats is given to prevent dehydration and undernutrition. Breast milk or preterm formula feeding via nasogastric tube can satisfactorily maintain caloric intake in small, sick, preterm infants, especially those with respiratory distress or recurrent apneic spells. Feedings are begun with small amounts (eg, 1 to 2 mL every 3 to 6 hours) to stimulate the gastrointestinal tract. When tolerated, the volume and concentration of feedings are slowly increased over 7 to 10 days. In very small or critically sick infants, total parenteral hyperalimentation via a peripheral IV or a percutaneously or surgically placed central catheter may be required for a prolonged period of time until full enteral feedings can be tolerated.

Hospital discharge

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

  • Taking an adequate amount of formula and/or breast milk without special assistance

  • Gaining weight steadily

  • Able to maintain a normal body temperature in a crib

  • No longer having apnea or bradycardia requiring intervention

Most preterm infants are ready to go home when they are at 35 to 37 weeks of gestational age and weigh 2 to 2.5 kg. However, there is wide variation. Some infants are ready for discharge earlier and some require longer stays in the hospital. The length of time the infant stays in the hospital does not affect the long-term prognosis.

Preterm infants should be transitioned to the supine sleeping position before hospital discharge. Parents should be instructed to keep cribs free of fluffy materials including blankets, quilts, pillows, and stuffed toys, which have been associated with an increased risk of sudden unexplained infant death (SUID).

Because preterm infants are at risk of apnea, oxygen desaturation, and bradycardia while in a car seat, the American Academy of Pediatrics currently recommends that before discharge all preterm infants have their oxygen saturation monitored for 90 to 120 minutes while seated in the car seat that they will use after discharge. However, there are no agreed-upon criteria for passing or failing the test, and a recent report from the Canadian Paediatric Society (CPS) found that the car seat test had poor reproducibility and did not predict risk of mortality or neurodevelopmental delay. Thus, the CPS does not recommend routine testing before discharge (1). Given the concerns about the car seat test, a common-sense approach to car travel is for a newly discharged preterm infant to be observed by a non-driving adult during all car seat travel until the infant has reached the due date and has remained consistently able to tolerate being in the car seat. Because the infant's color needs to be observed, travel should be limited to daylight hours. Long trips should be broken up into 45- to 60-minute segments so that the infant 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 only be given 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 (2).

After discharge, extremely preterm and very preterm infants should receive careful neurodevelopmental follow-up and appropriate early referral to intervention programs as needed for physical, occupational, and language therapy.

Treatment references

  1. 1. Narvey MR; Canadian Paediatric Society, Fetus and Newborn Committee: Assessment of cardiorespiratory stability using the infant car seat challenge before discharge in preterm infants (< 37 weeks' gestational age). Paediatr Child Health 21(3):155–162, 2016. doi: 10.1093/pch/21.3.155

  2. 2. Durbin DR, Hoffman BD; COUNCIL ON INJURY, VIOLENCE, AND POISON PREVENTION: Child Passenger Safety. Pediatrics 142(5):e20182460, 2018. doi: 10.1542/peds.2018-2460

Prognosis for Preterm Infants

Prognosis varies with presence and severity of complications, or the presence of multiple births, but usually mortality and likelihood of intellectual disability and other complications decrease greatly with increasing gestational age and birthweight (see table Neurodevelopmental Impairment in Extremely Preterm Infants).

Table
Table

Prevention of Preterm Delivery

Although early and appropriate prenatal care is important overall, there is no good evidence that such care or any other interventions decrease the incidence of preterm birth.

The use of tocolytics to arrest preterm labor and provide time for prenatal administration of corticosteroids to hasten lung maturation is discussed elsewhere (see Preterm Labor).

Key Points

  • There are many risk factors for preterm birth, but they are not present in most cases.

  • Complications include hypothermia, hypoglycemia, respiratory distress syndrome, apneic episodes, intraventricular hemorrhage, developmental delay, sepsis, retinopathy of prematurity, hyperbilirubinemia, necrotizing enterocolitis, and poor feeding.

  • Mortality and likelihood of complications decrease greatly with increasing gestational age and birthweight.

  • Treat disorders and support body temperature and feeding.

  • Although women who have consistent prenatal care have a lower incidence of preterm birth, there is no evidence that improved prenatal care or other interventions decrease the incidence of preterm birth.

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  1. National Highway Traffic Safety Administration: Car Seat Inspection (United States)

Late Preterm Infants

An infant born between 34 and 36 6/7 weeks of gestation is considered late preterm.

Complications of Late Preterm Infants

Although clinicians tend to focus on the more dramatic and obvious manifestations of problems of infants born < 34 weeks of gestation, late preterm infants are at risk of many of the same disorders (see complications of preterm infants). Compared to term infants, they have longer hospital stays and higher incidence of readmission and diagnosed medical disorders. Most complications relate to dysfunction of immature organ systems and are similar to, but typically less severe than, those of infants born more prematurely. However, some complications of prematurity (eg, necrotizing enterocolitis, retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage) are uncommon in late preterm infants. In most cases, complications resolve completely.

Complications more common among late preterm infants include the following:

  • Central nervous system: Apneic episodes (see Apnea of Prematurity)

  • Gastrointestinal tract: Poor feeding due to delayed maturation of the suck and swallow mechanism (primary reason for prolonged hospital stay and/or readmission)

  • Hyperbilirubinemia: Caused by immature mechanisms for hepatic bilirubin metabolism and/or increased intestinal reabsorption of bilirubin (eg, if feeding difficulties cause decreased intestinal motility)

  • Hypoglycemia: Caused by low glycogen stores

  • Temperature instability: Some degree of neonatal hypothermia in half of infants (caused by increased surface area to volume ratio, decreased adipose tissue, and ineffective thermogenesis from brown fat)

Evaluation of Late Preterm Infants

  • Routine screening for complications

There are variations in practice in the care of late preterm infants, particularly with respect to the gestational age and/or birthweight at which infants are routinely admitted to a NICU. Some hospitals routinely admit infants < 35 weeks of gestation to the NICU, whereas others may have a cutoff of < 34 weeks. Still other hospitals have a discretionary approach. Regardless of the location of the infant, all late preterm infants need close monitoring of the following:

  • Temperature: There is a high risk of hypothermia, and some late preterm infants may need to be in an incubator. The infant's temperature should be routinely assessed. For infants who are in the mother's hospital room, the temperature of the room should be maintained at 22 to 25° C (72 to 77° F), similar to that recommended for newborn care areas.

  • Weight: Depending on the infant's intake, there may be excessive weight loss, dehydration, and hypernatremia. The infant should be weighed daily and the percent weight loss should be calculated and tracked. Electrolytes should be checked if the weight loss exceeds 10%.

  • Feedings and intake: Late preterm infants may breastfeed or bottle feed poorly and take insufficient amounts of milk. Nasogastric feeding assistance is commonly needed, particularly in infants who are < 34 weeks of gestation. Because the mother's milk may take 1 to 4 days to come in, supplementation with donor milk or formula may be necessary. The amount of milk that the infant receives as well as either the number of wet diapers or the urine output (calculated as mL/kg/hour) should be tracked.

  • Glucose: Early hypoglycemia (within the first 12 hours of life) is common, so early feeding and blood glucose screening as recommended by the American Academy of Pediatrics (1) for the first 24 hours of life should be done. In addition, some experts recommend continued screening every 12 hours until discharge to detect infants with hypoglycemia due to insufficient milk intake.

Evaluation reference

  1. 1. Committee on Fetus and Newborn, Adamkin DH: Postnatal glucose homeostasis in late-preterm and term infants. Pediatrics 127(3):575–579, 2011. doi: 10.1542/peds.2010-3851

Treatment of Late Preterm Infants

  • Supportive care

  • Specific treatment for complications

Identified disorders are treated. For infants without specific conditions, support is focused on body temperature and feeding.

Late preterm infants can be stressed by the metabolic demands of maintaining a normal core temperature of 36.5 to 37.5° C (97.7 to 99.5° F), which roughly corresponds to an axillary temperature of 36.5 to 37.3° C (97.7 to 99.1° F). The environmental temperature at which metabolic demands (and thus calorie expenditure) to maintain body temperature in the normal range are lowest is the thermoneutral temperature. A normal core temperature can be maintained at lower environmental temperatures at the cost of increased metabolic activity, so a normal core temperature is no assurance that the environmental temperature is adequate. Once the core temperature falls below normal, the environmental temperature is below what is called the thermoregulatory range and therefore far below the thermoneutral range. In clinical practice, a room with a temperature of 22.2 to 25.6° C (72 to 78° F) combined with skin-to-skin contact under blankets, swaddling with multiple blankets, and wearing a hat may provide a thermoneutral environment for a large and somewhat more mature late preterm infant. Smaller and less mature late preterm infants usually require an incubator for a period of time to provide a thermoneutral environment.

Breastfeeding is strongly encouraged. Breast milk, which provides immunologic and nutritional factors that are absent in cow’s milk formulas, is well tolerated by late preterm infants. If infants do not suck and/or swallow adequately, feedings should be given by nasogastric gavage beginning with small amounts and gradually increasing over time.

Prognosis for Late Preterm Infants

Prognosis varies with presence and severity of complications. In general, mortality and the likelihood of complications decrease greatly with increasing gestational age and birthweight.

Respiratory issues typically resolve without long-term sequelae. Apneic episodes typically resolve when infants reach the age at which they would have been by 37 to 38 weeks of gestation and almost always by 43 weeks.

Neurodevelopmental disorders (see Childhood Development) are more common among late preterm infants (compared to full-term infants) assessed at 2 years of age and at kindergarten age (1). Early identification by monitoring developmental milestones and referring an intervention program for infants showing delays can be helpful.

Prognosis reference

  1. 1. Woythaler M: Neurodevelopmental outcomes of the late preterm infant. Semin Fetal Neonatal Med 24(1):54-59, 2019. doi: 10.1016/j.siny.2018.10.002

Key Points

  • Although late preterm infants (born between ≥ 34 weeks and < 36 6/7 weeks of gestation) may appear to be similar in size and appearance to term infants, they are at increased risk of complications.

  • Complications include hypothermia, hypoglycemia, poor feeding, excessive weight loss, respiratory distress, hyperbilirubinemia, and an increased likelihood of readmission after discharge.

  • Treat disorders and support body temperature and feeding.

  • Monitor neurodevelopmental status and provide appropriate referral to address any disabilities.

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