pediatrics
Preterm Infants
Late Preterm Infants
An infant born between 34 and 36 6/7 weeks of gestation is considered late preterm. 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 ). 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, 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) Neonatal Hyperbilirubinemia : Caused by immature mechanisms for hepatic bilirubin metabolism and/or increased intestinal reabsorption of bilirubin (eg, if feeding difficulties cause decreased intestinal motility) Neonatal Hypoglycemia : Caused by low glycogen stores Temperature instability: Some degree of Hypothermia in Neonates in half of infants (caused by increased surface area to volume ratio, decreased adipose tissue, and ineffective thermogenesis from brown fat) 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 ( Evaluation reference ) 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. 1.Committee on Fetus and Newborn, Adamkin DH: Postnatal glucose homeostasis in late-preterm and term infants.Pediatrics127(3):575–579, 2011. doi: 10.1542/peds.2010-3851 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 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.Woythaler M: Neurodevelopmental outcomes of the late preterm infant.Semin Fetal Neonatal Med24(1):54-59, 2019. doi: 10.1016/j.siny.2018.10.002 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. 