Late preterm infants

INTRODUCTION — Late preterm infants are born at a gestational age (GA) between 34 weeks and 0 days, and 36 weeks and 6 days. They have higher morbidity and mortality rates than term infants (GA ≥37 weeks) due to their relative physiologic and metabolic immaturity, even though they are often the size and weight of some term infants.

The epidemiology, outcomes, and management of late preterm infants will be reviewed here.

Specific disorders seen in late preterm infants and their management are discussed in greater detail separately:

●Hyperbilirubinemia (See "Unconjugated hyperbilirubinemia in neonates: Risk factors, clinical manifestations, and neurologic complications" and "Unconjugated hyperbilirubinemia in term and late preterm newborns: Screening" and "Unconjugated hyperbilirubinemia in term and late preterm newborns: Initial management".)

●Hypoglycemia (See "Pathogenesis, screening, and diagnosis of neonatal hypoglycemia" and "Management and outcome of neonatal hypoglycemia".)

●Breastfeeding issues (See "Breastfeeding the preterm infant", section on 'Late preterm infants'.)

DEFINITIONS — Medical terminology related to neonatal maturation is standardized according to gestational age (table 1), which permits appropriate care and comparison of data from different studies.

●Preterm birth – Preterm birth is defined as a delivery of an infant before completion of 37 weeks gestation by the World Health Organization (WHO), the American Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG). This occurs on or before the 259^th day after the first day of the last menstrual period (LMP) of the mother. (See "Prenatal assessment of gestational age, date of delivery, and fetal weight".)

●Late preterm infants – Late preterm birth is defined as birth between 34 weeks and 36 weeks and 6 days of gestation (ie, 239 to 259 days after the first day of the LMP) [1-3]. "Late preterm" has replaced "near term" to describe this group of infants, since the latter incorrectly implies that these infants are "close enough" to term and only require routine neonatal care [4].

●Early term infants – Early term infants are born at a GA between 37 and 38 6/7 weeks [1-3].

●Term infants – Term infants are born at a GA between 39 and 40 6/7 weeks [1-3].

●Late term infants – Late term infants are born at a GA between 41 and 41 and 6/7 weeks [1-3].

EPIDEMIOLOGY

Preterm birth rates — The overall preterm birth rate in the United States is approximately 10 percent, of which approximately three-quarters are late preterm (ie, late preterm births account for approximately 7.5 percent of all births in the US) (table 2).

Causes and risk factors — Preterm birth can occur spontaneously or because of medical or obstetrical indications for preterm delivery (labor induction or cesarean delivery).

Most late preterm births are associated with one or more of the following factors [3,5]. Additional risk factors for preterm birth are summarized in the table (table 3) and discussed separately. (See "Spontaneous preterm birth: Overview of risk factors and prognosis".)

●Obstetrical indications for delivery – Certain maternal, placental, and fetal conditions may result in medically indicated delivery at <37 weeks gestation if the risk of continuing pregnancy is assessed to be higher than the risk of late preterm delivery. (See "Induction of labor with oxytocin", section on 'Medical and obstetric indications' and "Cesarean birth: Preoperative planning and patient preparation", section on 'Indications'.)

●Multiple gestation pregnancies – In multiple gestation pregnancies, which are often associated with assisted reproductive technology (ART), delivery generally occurs earlier in gestation than for singleton pregnancies. (See "Assisted reproductive technology: Pregnancy and maternal outcomes".)

●Inaccurate gestational age estimation – Some late preterm births are a result of medically assisted deliveries of late preterm fetuses who were incorrectly thought to have reached term [6]. Prenatal gestational age may be determined by several methods and is discussed separately. (See "Prenatal assessment of gestational age, date of delivery, and fetal weight".)

●Advanced maternal age – Pregnant individuals who are ≥35 years old have an increased risk of preterm delivery compared with those who are between 21 and 24 years of age, even after accounting for other factors that are more common with advanced maternal age (eg, infertility, use of ART, maternal medical conditions). This issue is discussed separately. (See "Effects of advanced maternal age on pregnancy", section on 'Perinatal morbidity'.)

●Teen pregnancy – Teen pregnancy is also a risk factor for late preterm delivery [7]. (See "Pregnancy in adolescents", section on 'Pregnancy outcome'.)

●Assistive reproductive technology (ART) – The risk of spontaneous preterm birth appears to be elevated for ART pregnancies compared with those conceived spontaneously. This is discussed separately. (See "Assisted reproductive technology: Pregnancy and maternal outcomes", section on 'Spontaneous preterm birth'.) 

●Maternal chronic conditions – Compared with full-term infants, late preterm infants are more often born to mothers with chronic conditions including obesity, diabetes, hypertension, antepartum hemorrhage, lung disease, infection, cardiac disease, renal disease, genital herpes, and smoking [8,9]. (See "Obesity in pregnancy: Complications and maternal management", section on 'Indicated and spontaneous preterm birth' and "Infants of mothers with diabetes (IMD)", section on 'Prematurity' and "Chronic hypertension in pregnancy: Prenatal and postpartum care", section on 'Fetal/neonatal risks' and "Cigarette and tobacco products in pregnancy: Impact on pregnancy and the neonate", section on 'Preterm birth'.)

BIRTH HOSPITALIZATION

Common neonatal complications — Clinicians who care for late preterm infants should be aware that this population is at increased risk for neonatal morbidity and mortality. They should be familiar with the associated neonatal complications of late preterm birth and provide appropriate intervention, if warranted. During the birth hospitalization, late preterm infants are at increased risk for the following complications [8-13]:

●Hypothermia

●Hypoglycemia

●Respiratory distress

●Apnea

●Hyperbilirubinemia

●Feeding difficulties

●Low Apgar scores (<4)

●Neurologic morbidity (eg, seizure, perinatal asphyxia)

The risk of complications increases if there are additional risk factors for neonatal morbidity (eg, maternal diabetes or hypertension). In a population-based study that compared 26,170 late preterm infants with 377,638 term infant, neonatal morbidity was seven times greater in late preterm than term infants (22 versus 3 percent) [9]. Neonatal morbidity rates increased with increasing numbers of maternal risk factors (18 percent with no maternal risk factors, 29 percent with one, and 37 percent with two). Maternal conditions that increased morbidity for late preterm infants included hypertensive disorders of pregnancy, diabetes, antepartum hemorrhage, lung disease, infection, cardiac disease, renal disease, and genital herpes.

Hypothermia — Late preterm infants are more susceptible to hypothermia compared with term infants, as they have less white adipose tissue for insulation, cannot generate heat as effectively from brown adipose tissue, and lose heat more readily due to their larger ratio of surface area to weight [10,11,14,15].

Hypoglycemia — The risk of hypoglycemia is reported to be three to seven times greater in late preterm infants than in term infants [8,10,16]. The incidence of hypoglycemia increases with decreasing gestational age. (See "Pathogenesis, screening, and diagnosis of neonatal hypoglycemia" and 'Respiratory morbidity' below.)

Respiratory morbidity — Late preterm infants are at greater risk than term infants for respiratory morbidity, including respiratory distress syndrome (RDS), transient tachypnea of the newborn, pneumonia, respiratory failure, and the need for ventilator support [8,10,12,17]. Respiratory morbidity increases with decreasing gestational age.

In a population-based Swedish study of approximately 1.7 million live-born singleton births born between 1998 and 2016, late preterm infants (3.2 percent of the birth cohort) compared with the reference full-term infants defined as a gestational age (GA) of 39 to 40 weeks (56.6 percent cohort) had a greater risk for any respiratory morbidity (adjusted relative risk [aRR] 5.54, 95% CI 5.24-5.85), transient tachypnea (aRR 4.76, 95% CI 4.47-5.08), RDS (aRR 46.53, 95% CI 38.59-56.10), and pneumothorax (aRR 2.99, 95% 2.50-3.58) [8].

The increased risk of respiratory morbidity in late preterm infants is related to immature lung structure and decreased surfactant production, as lung development of the terminal respiratory sacs and alveoli continues beyond gestational weeks 34 to 36. This delayed pulmonary maturation increases the risk of RDS, especially for infants of mothers who did not receive antenatal steroids [10,11,18]. Since biochemical changes during labor enhance fetal lung maturation and clearance of pulmonary fluid, and retained fluid can inactivate surfactant, infants born via cesarean delivery without labor are more likely to have RDS [19]. (See "Respiratory distress syndrome (RDS) in the newborn: Clinical features and diagnosis".)

Transient tachypnea (retained fetal lung fluid) and persistent pulmonary hypertension of the newborn are other causes of respiratory distress seen in late preterm infants [6,11,20]. Late preterm infants are at increased risk for respiratory failure and are more likely than term infants to require extracorporeal membrane oxygenation (ECMO) support, with a greater risk of subsequent mortality and morbidity [21,22]. (See "Overview of neonatal respiratory distress and disorders of transition" and "Transient tachypnea of the newborn" and "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis".)

Apnea — The reported incidence of apnea in late preterm infants (4 to 7 percent) is greater than in term infants (1 to 2 percent) [10,14,23,24]. Late preterm infants are also at increased risk for sudden infant death syndrome (SIDS) compared with term infants. (See "Pathogenesis, clinical manifestations, and diagnosis of apnea of prematurity" and "Sudden infant death syndrome: Risk factors and risk reduction strategies", section on 'Infant risk factors'.)

Hyperbilirubinemia — Due to immaturity of hepatic bilirubin conjugation pathways, late preterm infants are more likely than term infants to have prolonged jaundice with significantly elevated unconjugated serum bilirubin at five days of age [8,11,25,26]. In the population-based Swedish study described above, the risk of neonatal jaundice was 12.5-fold greater for late preterm infants compared with the reference group of full-term infants [8]. Feeding difficulties also can lead to a delay in the resolution of enterohepatic recirculation of bilirubin, also contributing to an increase in serum bilirubin.

Hyperbilirubinemia is the most common reason for neonatal readmission for late preterm infants [27]. At a given serum bilirubin concentration, the risks for bilirubin-induced brain injury and kernicterus are greater in late preterm infants compared with term infants due to the relative immaturity of the blood-brain barrier, lower circulating bilirubin-binding albumin concentrations, and higher risk of concurrent illness [27,28]. (See 'Readmissions after the birth hospitalization' below and "Unconjugated hyperbilirubinemia in neonates: Etiology and pathogenesis" and "Unconjugated hyperbilirubinemia in term and late preterm newborns: Initial management".)

Breastfeeding difficulties — Breastfeeding remains the optimal feeding choice for late preterm infants because of the benefits to both mother and infant [29]. However, late preterm infants require additional monitoring and support compared with term infants because their oro-buccal strength and coordination of swallowing/breathing mechanisms are not fully matured [10,11,29]. As a result, mothers of late preterm infants will need to express milk to fully establish their milk supply, and their infants will benefit from early supplementation.

Difficulty in establishing successful feeding increases the risk of readmission for dehydration and neonatal hyperbilirubinemia [10,30,31]. (See "Breastfeeding the preterm infant", section on 'Late preterm infants'.)

Discharge criteria — Prior to hospital discharge, parents/caregivers should be informed about common problems that late preterm newborns may experience. These include (see 'Common neonatal complications' above):

●Hyperbilirubinemia (see "Unconjugated hyperbilirubinemia in neonates: Risk factors, clinical manifestations, and neurologic complications")

●Feeding difficulties (see "Breastfeeding the preterm infant", section on 'Late preterm infants' and "Neonatal oral feeding difficulties due to sucking and swallowing disorders")

●Dehydration (see "Overview of the routine management of the healthy newborn infant", section on 'Weight loss' and "Initiation of breastfeeding", section on 'Warning signs of insufficient intake')

Predischarge teaching should be provided so that parents/caregivers can recognize these conditions and seek appropriate care after hospital discharge.

We concur with the American Academy of Pediatrics (AAP) guidelines for discharge criteria for late preterm infants, most of whom will not be ready for discharge before 48 hours [11]:

●Determine the accurate gestational age and ensure that there are no abnormalities or medical conditions (ie, poor feeding and/or hyperbilirubinemia) that require further hospitalization.

●The infant should demonstrate physiologic stability by showing competency in the following:

•Maintaining thermoregulation, defined as an axillary temperature of 36.5 to 37.4ºC (97.7 to 99.3ºF), in an open crib.

•Feeding, defined as coordinated sucking, swallowing, and breathing while feeding, and weight loss not to exceed 7 percent of birth weight during birth hospitalization (or 2 to 3 percent per day). If the infant is breastfed, at least twice daily documented observation by trained caregivers of successful position, latch, and milk transfer also should be performed [31]. (See "Breastfeeding the preterm infant", section on 'Late preterm infants'.)

•Maintaining cardiorespiratory control with stable vital signs of a respiratory rate less than 60 breaths per minute and a heart rate between 100 and 160 beats per minute, and absence of medical illness.

•Passing at least one stool spontaneously.

●Completion of other routine newborn care, including (see "Overview of the routine management of the healthy newborn infant"):

•Screening tests (including hearing screening, bilirubin screening, "blood spot" screening panel, screening for hypoglycemia, and pulse oximetry screening for critical congenital heart disease) (see "Overview of the routine management of the healthy newborn infant", section on 'Routine newborn screening')

•Hepatitis B vaccine (see "Hepatitis B virus immunization in infants, children, and adolescents", section on 'Routine infant immunization')

•Vitamin K prophylaxis and newborn eye care for prevention of gonococcal ophthalmia neonatorum (see "Overview of the routine management of the healthy newborn infant", section on 'Vitamin K' and "Overview of the routine management of the healthy newborn infant", section on 'Eye care')

●Assessment of the family and home environment to identify any risk factors that may have an impact on the health of the infant. As noted below, these infants may be at higher risk for maternal tobacco smoke exposure, non-supine sleep position, and lack of breastfeeding [32]. (See 'Readmissions after the birth hospitalization' below.)

●Successful training of the parents who have demonstrated competency in the care of their infant and the ability to assess for hyperbilirubinemia, feeding difficulties, and dehydration.

●A follow-up visit for 24 to 48 hours after discharge is scheduled with an identified primary care provider. (See 'Primary care follow-up' below.)

●The role of the car seat test prior to discharge is discussed below. (See 'Car seat tolerance testing' below.)

The National Perinatal Association (NPA) multidisciplinary guidelines for the care of late preterm infants is an excellent resource to guide management during hospitalization and transition to home [33]. Links to the NPA and AAP guidelines and other society guidelines are provided separately. (See 'Society guideline links' below.)

Because late preterm infants are more likely than term infants to have complications that require medical attention, they generally require a longer length of stay for the birth hospitalization, which results in higher health care costs [32,34-36]. In a retrospective study that analyzed data from a cohort of commercially insured neonates in the United States from 2005 to 2016, late preterm infants had a longer average birth hospital stay (median 4 versus 2 days) with seven-fold higher costs of care [36].

Car seat tolerance testing — It remains uncertain whether late preterm infants are at increased risk for cardiopulmonary events when placed in a car seat. In our center, a car seat tolerance test is performed for late preterm infants prior to discharge along with educating parents and caregivers about the potential risk of cardiopulmonary events in an upright position. If an infant does not pass the car seat screen but is otherwise clinically stable, discharge is allowed with the advice to the family/caregivers that an adult be seated in the back seat of the car to visually monitor the infant during travel. All families are advised to limit time in the upright position.

The concern for cardiopulmonary events in the car seat position was highlighted by a study of 918 late preterm infants that reported a 5 percent initial failure rate for a car seat screening test [37]. The risk of failure was associated with respiratory findings of obstructive apnea and oxygen desaturations and admission to a neonatal intensive care unit (NICU) during a portion of the birth hospitalization. In the United States, although most newborn nurseries perform a predischarge car seat screening test, there is a large degree of variability in implementation [38]. While car seat testing for late preterm infants remains advisable, further study is needed to provide guidance on determining which infants would most benefit from screening and failure criteria. (See "Discharge planning for high-risk newborns", section on 'Car seat/bed use'.)

PRIMARY CARE FOLLOW-UP — Primary care for late preterm infants encompasses routine primary care (eg, immunization, anticipatory guidance, and monitoring of growth and development) and identifying infants at risk for jaundice, feeding difficulties, and dehydration [11].

We advise weekly weight checks initially to assess growth using an initial target growth velocity of at least 20 g/day. During this time, dietary adjustments can be made to maintain adequate growth. Once adequate weight gain is established without need for supplementation or fortification, the frequency of visits can be decreased.

The usual caloric intake for adequate growth during the weeks after hospital discharge is approximately 100 to 130 kcal/kg per day. Although otherwise healthy late preterm infants are able to learn to breastfeed, they often experience more difficulty than term infants in establishing successful latch and milk transfer. To maintain adequate caloric intake, they usually require supplementation, optimally with expressed maternal milk. Thus, it is crucial to support early establishment of the maternal milk supply, beginning within the first hour after delivery if at all possible. (See "Breastfeeding the preterm infant", section on 'Late preterm infants' and "Growth management in preterm infants", section on 'Routine nutrient supplementation'.)

If there is insufficient maternal milk volume to support adequate growth, donor human milk or formula may be used to supplement feeds. It remains uncertain whether the use of nutrient-enriched formula (transitional preterm formula) is beneficial after hospital discharge either for infants who require supplemental use or for exclusively formula-fed infants. (See "Growth management in preterm infants", section on 'Formula-fed infants'.)

Human milk-fed preterm infants should also receive iron and vitamin D supplementation, as they are not adequately supplied in human milk alone. (See "Iron deficiency in infants and children <12 years: Screening, prevention, clinical manifestations, and diagnosis", section on 'Recommendations for iron supplementation' and "Vitamin D insufficiency and deficiency in children and adolescents", section on 'Prevention in the perinatal period and in infants'.)

READMISSIONS AFTER THE BIRTH HOSPITALIZATION — Approximately 4 to 6 percent of late preterm infants are readmitted to the hospital within 30 days of discharged from the birth hospitalization, a rate that is two- to three-fold higher than for infants born at term [36,39]. They continue to have greater health care needs and utilization than term infants throughout the first year of life and even in later childhood [34,40-43].

The most common causes for readmission in the neonatal period included jaundice, feeding difficulties, and dehydration [42]. In later infancy or childhood, respiratory illnesses (asthma, bronchiolitis, pneumonia) were the most common reasons for hospitalization [42].

In addition to the increased vulnerability of late preterm infants due to their prematurity, environmental factors may contribute to the increased risk of morbidity in this population. For example, in a study that analyzed data from the Centers for Disease Control and Prevention's (CDC) Pregnancy Risk Assessment Monitoring System from 2000 to 2008, late preterm infants were more likely to be exposed to maternal tobacco smoke, less likely to be placed in a supine sleep position, and less likely to be breastfed both initially and over time [32]. These factors are known risk factors for respiratory illnesses and sudden infant death. (See "Secondhand smoke exposure: Effects in children", section on 'Effects in childhood' and "Sudden infant death syndrome: Risk factors and risk reduction strategies", section on 'Sleep position and environment' and "Infant benefits of breastfeeding", section on 'Prevention of illnesses while breastfeeding'.)

OUTCOMES

Mortality — Late preterm birth appears to be associated with a modest increase in risk of infant mortality compared with term birth [3,5,44]. The impact of late preterm birth on mortality is substantially less than that of earlier preterm birth (ie, <32 weeks gestational age [GA]). Nevertheless, approximately 8 percent of all neonatal deaths in the United States occur in late preterm infants [45]. The risk of neonatal and infant mortality increases with decreasing gestational age [3,5,44]. For example, infants born at 36 weeks GA have an approximately 2.5-fold higher risk of infant mortality compared with term infants, whereas infants born at 34 weeks GA have a 6-fold higher risk. There also appears to be a slightly increased risk of early mortality in adulthood [46,47].

Neurodevelopmental outcome — Observational studies reporting on long-term neurodevelopmental outcomes in late preterm infants have reached variable conclusions. Many studies reported that individuals born late preterm and/or early term, compared with those born at term, are at increased risk for neurodevelopmental impairment, even after adjusting for confounding factors [13,44,46,48-54]. Adverse outcomes reported in these studies include:

●Cognitive impairment (ie, lower scores on standardized cognitive testing) [13,46,51].

●Lower academic achievement [48,50,54].

●Motor impairment, including cerebral palsy [13,44].

●Psychiatric and behavioral disorders (eg, attention deficit hyperactivity disorder (ADHD)) [46,51,52].

●Sensory impairments (eg, vision and hearing loss) [13].

However, other studies have not detected an association between late preterm birth and adverse neurodevelopmental outcomes [55,56]. For example, in a study that included 256 individuals born late preterm and 4419 individuals born at term, rates of ADHD and other learning disabilities by age 19 years were similar in both groups (20 versus 19 percent, respectively) [56]. In a prospective study that followed 53 healthy late preterm infants into childhood, standardized assessments of cognition, achievement, social skills, and behavioral/emotional problems were similar to those of term infants [55].

The different findings in these studies may be explained, at least in part, to differences in study design (evaluation tools, timing of assessment, and outcome definition) and changes in perinatal care over time. (See "Long-term neurodevelopmental impairment in infants born preterm: Epidemiology and risk factors", section on 'Limitations of the data'.)

Brain immaturity at birth may affect outcomes for some individuals who were born late preterm. Although data are limited on the brain maturation of late-preterm infants, autopsy and magnetic resonance imaging demonstrate that at 35 weeks gestation, the brain weighs 65 percent of a full-term infant's brain, and the external surface has fewer sulci [57,58]. This immaturity may increase the brain's vulnerability to long-term injury.

Other potential long-term effects — It remains uncertain whether late preterm birth has other long-term effects. Some data suggest that children who are born late preterm may be at risk for poor weight gain during infancy, long-term respiratory morbidity (eg, asthma), and chronic kidney disease [46,59-64]. Studies evaluating adult outcomes of late preterm infants have shown increased risk of type 2 diabetes mellitus and stroke and slightly lower educational and/or occupational attainment compared with individuals born at term [46].

PREVENTION — Prevention is one of the keys to decreasing the mortality and morbidity associated with late preterm births. An important component of prevention is to avoid induced vaginal or planned cesarean delivery before 39 weeks gestation (as determined by preinduction assessment) unless medically indicated. (See "Spontaneous preterm birth: Overview of risk factors and prognosis" and "Prenatal assessment of gestational age, date of delivery, and fetal weight" and "Induction of labor with oxytocin".)

In addition, further research is needed to refine the management of the fetus and mother at late preterm gestation, such as better identification of pregnancies that require early delivery for medical conditions [65]. Areas of research include [4]:

●Assess the risk/benefit ratio for diagnosis-specific indications for late preterm delivery, such as more accurate estimation of fetal well-being and outcome in the presence of maternal diseases (eg, hypertension and diabetes).

●Identify management strategies to improve specific outcomes in late preterm infants. One proposed strategy under investigation is the use of antenatal steroids in late preterm pregnancies.

●Improve the precision of determining gestational age.

●Improve the ability to identify the fetus at risk for late-pregnancy intrauterine demise (ie, stillbirth). (See "Stillbirth: Incidence, risk factors, etiology, and prevention", section on 'Strategies for preventing a first stillbirth in the general obstetric population'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Late preterm infants".)

SUMMARY AND RECOMMENDATIONS

●Definition – Late preterm infants are those with a gestational age (GA) from 34 weeks and 0 days to 36 weeks and 6 days. They have a higher risk of morbidity and mortality compared with full-term infants. (See 'Definitions' above and 'Outcomes' above.)

●Birth hospitalization – Late preterm infants generally require a longer stay during the birth hospitalization compared with term infants. (See 'Birth hospitalization' above.)

•Complications – The most common complications during the birth hospitalization include hypothermia, hypoglycemia, respiratory distress, apnea, hyperbilirubinemia, and feeding difficulties. The risk of these complications increases if there are additional maternal conditions (eg, maternal diabetes and hypertension). (See 'Common neonatal complications' above.)

•Management – Management during the birth hospitalization focuses on establishing successful feeding and monitoring for common complications (see 'Birth hospitalization' above):

-Feeding support (see 'Breastfeeding difficulties' above and "Breastfeeding the preterm infant", section on 'Late preterm infants')

-Hyperbilirubinemia (see 'Hyperbilirubinemia' above and "Unconjugated hyperbilirubinemia in term and late preterm newborns: Screening" and "Unconjugated hyperbilirubinemia in term and late preterm newborns: Initial management")

-Hypoglycemia (see 'Hypoglycemia' above and "Pathogenesis, screening, and diagnosis of neonatal hypoglycemia", section on 'Screening' and "Management and outcome of neonatal hypoglycemia")

-Respiratory complications (eg, transient tachypnea of the newborn, respiratory distress syndrome, apnea of prematurity) (see "Transient tachypnea of the newborn" and "Respiratory distress syndrome (RDS) in preterm infants: Management" and "Management of apnea of prematurity")

●Readmission after birth hospitalization – Following discharge from the birth hospitalization, late preterm infants are at increased risk for readmission compared with term infants. The most common reasons for readmission include jaundice, feeding difficulties, dehydration, and respiratory problems (asthma, bronchiolitis, pneumonia). Some of these readmissions can be prevented by initial monitoring; early establishment of maternal milk production, with supplementation in addition to direct feeding at breast; early outpatient follow-up; and support for families to provide appropriate home care after discharge. (See 'Readmissions after the birth hospitalization' above.)

●Mortality and long-term morbidity

•Mortality – Late preterm birth appears to be associated with a modest increase in risk of infant mortality compared with term birth; the risk increases with decreasing GA. There also appears to be a slightly increased risk of early mortality in adulthood. (See 'Mortality' above.)

•Neurologic impairment – Many studies have reported that compared with individuals born at term, those born late preterm at increased risk for long-term neurodevelopmental impairment (cognitive impairment, motor impairment, vision and hearing loss, lower academic achievement, mental health disorders [eg, attention deficit hyperactivity disorder]). However, other studies have not detected an association between late preterm birth and adverse neurodevelopmental outcomes. (See 'Neurodevelopmental outcome' above.)

•Other long-term morbidities – Long-term health problems that have been reported to occur more commonly in individuals born late preterm compared with those born at term include (see 'Other potential long-term effects' above):

-Poor weight gain during infancy

-Childhood asthma

-Type 2 diabetes mellitus (in adulthood)

-Stroke (in adulthood)

ACKNOWLEDGMENT — One of the authors of this topic (Dr. Barfield) is employed by the Centers for Disease Control and Prevention (CDC). The opinions expressed herein are those of the authors and do not represent the official position or policy of the CDC.