When the growth of a low-birth-weight (LBW) infant is evaluated, the data should be recorded based on his or her gestational (corrected) age, rather than his or her postnatal age. Growth parameters should be plotted on standard growth curves using the corrected age until approximately 2 years of age, when the age difference becomes insignificant. From birth to 2 years of age, use the WHO growth charts (5). After 2 years of age, use the standard CDC growth charts (6). Patterns of growth emerge from groups of patients who generate recognizable patterns specific to their group (5,6).

Healthy, LBW, AGA infants generally experience catch-up growth during the first 2 years of life. Little catch-up growth occurs after 3 years of age. Head circumference usually is the first parameter to demonstrate catch-up growth and often plots at a higher percentile than do weight and length. Increases in weight are followed within several weeks by increases in length. Rapid catch-up head growth must be distinguished from pathologic growth associated with hydrocephalus. An imaging study may be indicated if the infant’s history or symptoms suggest hydrocephalus. More commonly, if neurologically intact, extra-axial fluid “benign hydrocephalus” is the cause and usually of no significant concern (7). Insufficient brain growth, a head circumference falling more than 2 standard deviations below the mean, often indicates that the infant is at risk for significant developmental disability.

Growth velocities for weight and height vary considerably. Some preterm infants show growth on curves between the 75th and 97th percentiles by 3 months of corrected age, whereas others remain on low curves well beyond their 1st year. It is helpful to evaluate an infant’s weight gain in comparison to gains in length. Low weight gain compared with increase in length or a decline in all growth parameters suggests inadequate nutrition. Weight percentiles significantly greater than length percentiles indicate obesity. Obesity may occur in a preterm infant whose parents overfeed their previously underweight baby. It is not uncommon to see an infant who was formerly failing to thrive rather abruptly become obese when the medical problems resolve, but the diet remains high in calories.

Growth of the small for gestational age (SGA) infant is influenced strongly by the cause of the intrauterine growth restriction. Overall, LBW-SGA infants demonstrate less catch-up growth than LBW-AGA infants, but if they do manifest catch-up, acceleration starts by 8 to 12 months of corrected age (1). Approximately 50% of LBW-SGA infants are below average in weight at 3 years of age, whereas only 15% of LBW-AGA infants remain below average weight at the same age (4). Symmetric SGA infants, with birth head circumference at a similar percentile as birth weight, are less likely to demonstrate catch-up growth than are asymmetric SGA infants, whose birth head circumference was at a significantly higher percentile than their weight (head sparing). As with AGA infants, head circumference is normally the first parameter to demonstrate catch-up, followed by weight and then by length.

Because of the wide range of growth that is considered normal during the first several years of life, it is best to analyze trends in growth rather than make assumptions based on single measurements. When abnormalities are noted in growth trends, the history of the infant’s nutritional status during hospitalization, results of cranial sonography studies, and the status of continuing illnesses should be sought to identify a possible cause.

Traditionally, although somewhat controversial, the goal for preterm infants is to achieve a growth rate approximating that expected while in utero had they not been born prematurely (4) (see also Chapter 20). Because weight gain is suboptimal during acute illness, all efforts should be made to promote catch-up growth once the medical condition is stable. The nutritional needs of the preterm infant during the first few months of life exceed those of a term neonate and may continue for the entire first year of life even if
there are no exceptional medical or feeding problems. Appropriate choices for many preterm infants include breast milk and routine infant formulas, but because many preterm infants continue to have increased caloric requirements, breast milk and routine formulas often need to be supplemented with either carbohydrates or fats. Alternatively, formulas can be concentrated somewhat to increase their caloric density, allowing the infant to consume more calories per unit volume. Powdered formula can be added to breast milk to help increase the caloric content when offered by bottle. There are also commercially available premature growth formulas tailored to address the unique protein, fat, and caloric needs of the growing preterm infant for the first year of life (8,9,10,11). These are 22 kcal/oz formulations. Most infants do not tolerate feedings with caloric densities greater than 27 kcal/oz. Infants given feedings concentrated beyond 24 kcal/oz should be monitored for symptoms of intolerance such as vomiting and diarrhea and for hyperosmolar dehydration secondary to insufficient free water intake. Whole cow’s milk is poorly tolerated and should be avoided. When caloric additives or concentrated formulas are used, care should be taken to maintain an appropriate caloric distribution of nutrients with a ratio among carbohydrates-fats-protein of approximately 40-50-10 (8,9).

Caloric requirements for adequate growth vary. Healthy preterm infants generally require 110 to 130 kcal/kg/d, but some infants with chronic disease may require up to 150 kcal/kg/d (12). Caloric intake should be increased as tolerated until weight gain is satisfactory.

Often, infants with ongoing illness or those just recovering from their long hospitalization will be unable to consume the volume of formula or breast milk needed to provide them with the calories they need for catch-up or even maintenance of their ideal growth rate. It is not uncommon to suggest offering up to one-half of the daily calculated nutritional needs by continuous tube feeding through the night, allowing the infant to take the remaining requirement orally during the day. Taking this approach decreases the need and energy for the infant to consume large-volume feedings orally and allows gradual increase in volume per feed as tolerated during the day, balanced by gradual decrease in the total volume of overnight tube feeding (13).

The American Academy of Pediatrics (AAP) recommends that full doses of DTaP vaccine be administered to prematurely born infants at the appropriate postnatal, that is, chronologic age. A large percentage of preterm infants demonstrate inadequate protection if given a reduced dosage of DTaP vaccine at the routine intervals. Fewer side effects occur in preterm infants who receive full-dose vaccine than in their full-term counterparts, and the use of acellular pertussis vaccine should obviate any concerns in this regard. The same contraindications to immunizing full-term infants against pertussis apply to preterm infants. Most importantly, infants with BPD are at highest risk for serious sequelae if they contract pertussis. Therefore, the pertussis component of this vaccine should not be withheld. Similarly, the pertussis component should not be withheld in any child with cerebral palsy or other muscle tone abnormalities. If an infant has an underlying seizure disorder, the decision to withhold pertussis should be reviewed with a pediatric neurologist.

The AAP Committee on Immunization Practices recommends that full-dose inactivated, enhanced potency polio (IPV), Haemophilus influenzae type b (Hib), pneumococcal, varicella, rotavirus, and measles-mumps-rubella (MMR) vaccines be administered at the appropriate chronologic age.

Infants with chronic pulmonary disease (e.g., BPD) or cardiac disease with pulmonary vascular congestion are at high risk for the
development of serious illness if infected with an influenza virus (18). Infants with influenza have presented with symptoms of sepsis, apnea, and lower airways disease. To protect vulnerable infants, immunization with influenza vaccine is indicated for household contacts, including siblings, primary caretakers, home care nurses, and hospital personnel. For infants older than 6 months of chronologic age, two doses of split virus vaccine should be given 1 month apart between October and December, followed by an annual dose. It is now recommended that influenza vaccine be given to all infants under 2 years of age (17,18). Older siblings under 9 years of age who have not received previous influenza vaccines also require two doses initially. However, adults and older siblings with natural immunity or who have received previous immunizations need only one yearly dose.

Preterm infants, especially those with underlying CLD, are particularly at risk for serious sequelae after becoming infected with respiratory syncytial virus (RSV) during the late fall and winter months. Many will require rehospitalization and reintubation for respiratory failure, and they are often left with an exacerbation of their CLD requiring increased support with supplemental oxygen, bronchodilators, and/or diuretics. Many develop asthma during childhood over and above what may be associated with just having BPD itself (19). Attempts to develop a vaccine against RSV have been unsuccessful; however, an anti-RSV monoclonal antibody (Palivizumab Synagis) has been approved for use in high-risk infants. Monthly intramuscular injections are necessary to provide passive protection throughout the RSV season. Synagis is expensive; thus, its use should be limited to those infants most at risk. According to the 2014 guidelines set forth by the AAP (20), those who should be considered to receive monthly injections include the following:

For infants with birth weights below 2,000 g born to hepatitis B surface antigen-negative women, it is advised to delay the initiation of hepatitis B vaccine until just before initial hospital discharge, provided the infant weighs more than 2,000 g or has reached 1 month of age (18).

Retinopathy of prematurity (ROP) (see also Chapter 50) is a disorder that interrupts the normal vascularization of the developing retina in preterm infants that potentially can lead to blindness in a small, but significant, percentage of those infants. ROP is mainly a disease associated with prematurity and, in particular, with those who are less than 30 weeks’ gestation. The incidence and severity of ROP increase with decreasing gestational age. Most cases of ROP resolve spontaneously, but even with complete resolution, scarring of the retina may occur. Generally, the more severe the disease, the longer it takes for resolution. An infant with ROP affecting Zone 1, however, is at a much greater risk for permanent visual sequelae than one who has the disease affecting Zone 2 or 3 (21). According to recommendations in the AAP Guidelines for Perinatal Care (22), infants with a birth weight of less than or equal to 1,500 g or with a gestational age of 30 weeks or less and selected infants between 1,500 and 2,000 g or greater than 30 weeks’ gestation with an unstable clinical course who are believed to be at high risk by their attending pediatrician or neonatologist should have an ophthalmologic examination for ROP. The timing of the initial examination is based on postmenstrual age and postnatal (chronologic) age, to detect ROP before it becomes severe enough to result in retinal detachment. A schedule of follow-up visits is based on the retinal findings and should be determined by the examining ophthalmologist. All infants with immature fundi or any stage of ROP require close monitoring until the eyes have matured or the ROP has completely resolved. Regardless of whether an infant had ROP or not, this population remains at risk for other visual disorders such as strabismus, amblyopia, high refractive errors, and cataracts. Follow-up for these potential problems after discharge from the NICU is indicated within 4 to 6 months after discharge, at 1 year of age, and again prior to school entrance.

Services for visually impaired children are available at county and state levels. Early identification and referral of a child with visual handicaps to such programs is essential to provide the child and family with the services and resources they need.

The incidence of sensorineural hearing loss in preterm or high-risk infants graduating from an NICU is generally reported to be between 1% and 6%. Several factors place these infants at particular risk for hearing loss, including hypoxia, hyperbilirubinemia, infections, unstable blood pressure, environmental noise, and ototoxic drugs. According to the Joint Committee on Infant Hearing Year 2007 Position Statement, where the Universal Newborn Hearing Screening (UNHS) Program is described, all infants should have access to hearing screening using a physiologic measure before hospital discharge (23). Auditory brainstem response (ABR) testing is the only appropriate screening technique for use in the NICU, since otoacoustic emission (OAE) testing alone will not pick up neural conduction disorders or auditory neuropathy spectrum disorder (NASD). For infants who do not pass automated ABR testing in the NICU, referral should be made directly to an audiologist for rescreening and, when indicated, comprehensive evaluation, including diagnostic ABR testing, rather than for general outpatient rescreening. All infants with confirmed permanent hearing loss should receive services before 6 months of age in interdisciplinary intervention programs that recognize and build on strengths, informed choice, traditions, and cultural beliefs of the family.
All infants who pass newborn hearing screening but who have risk indicators for other auditory disorders and/or speech and language delay should receive ongoing audiologic and medical surveillance and monitoring for communication development. Infants with indicators associated with late-onset, progressive, or fluctuating hearing loss and/or brainstem auditory pathway dysfunction should have follow-up monitoring.

All infants, regardless of newborn hearing screening outcome, should receive ongoing monitoring for development of age-appropriate auditory behaviors and communication skills. Any infant who demonstrates delayed development of auditory and/or communication skills, even if he or she passed newborn hearing screening, should receive an audiologic evaluation to rule out a hearing loss.

Once a child is sitting without support, reliable behavioral hearing tests can be performed. See decibel (dB) levels that determine level of hearing impairment in Table 55.1. Lack of response to sound levels greater than a 15 dB is indicative of some degree of hearing loss. Evaluation by a pediatric otolaryngologist may be indicated to rule out an underlying cause such as increased middle ear fluid rather than a sensorineural cause.