Assessment parameters

Gestational age in the newborn

Obtaining an accurate assessment of gestational age begins with the prenatal history and birth history and can assist the health care provider in anticipating conditions associated with preterm birth. The prenatal assessment includes a maternal history of the last menstrual period, history of prenatal care, maternal weight gain and general health during pregnancy, maternal infections, hypertension, history of toxemia or other complications of pregnancy, and history of substance abuse or physical abuse. The birth history includes history of the onset and length of labor and the progression and method of delivery (see Chapter 4).

The New Ballard Score (NBS) (Figure 2-1) is the tool most often used to evaluate the gestational age of newborn infants. The NBS is a valid tool and accurately assesses gestational age for extremely low birth weight infants ≤1000 g or extremely premature infants from 20 weeks to term infants from 40 to 44 weeks of gestation.¹ The NBS is a revision of the original Dubowitz scale, which was used to determine gestational age of infants 35 to 42 weeks of age. The NBS consists of six physical and six neuromuscular criteria for assessing maturity. The criteria for extremely preterm infants correlates with 1 and 0 on the scale. Gestational age must be determined within 48 hours after birth except in the case of the extremely preterm infant or extremely low birth weight infant whose age should be determined within 12 hours after birth. Assessment of neuromuscular maturity score should be repeated within 48 hours after birth if neonatal asphyxia or maternal anesthesia may have affected initial assessments (Box 2-1).

BOX 2-1

Tests for Assessing Neuromuscular Maturity in the Newborn

Posture.

With infant quiet and in supine position, observe degree of flexion in arms, legs. Muscle tone and degree of flexion increase with maturity. Full flexion of the arms, legs = 4.

Square window.

With thumb supporting back of arm below wrist, apply gentle pressure with index and third fingers on dorsum of hand without rotating infant’s wrist. Measure angle between base of thumb and forearm. Full flexion (hand lies flat on ventral surface of forearm) = 4.

Arm recoil.

With infant supine, fully flex forearms on upper arms, hold for 5 seconds; pull down on hands to fully extend and rapidly release arms. Observe rapidity and intensity of recoil to state of flexion. A brisk return to full flexion = 4.

Popliteal angle.

With infant supine and pelvis flat on firm surface, flex lower leg on thigh, then flex thigh on abdomen. While holding knee with thumb and index finger, extend lower leg with index finger of other hand. Measure degree of angle behind knee (popliteal angle). Angle of <90 degrees = 5.

Scarf sign.

With infant supine, support head in midline with one hand; use other hand to pull infant’s arm across shoulder so that infant’s hand touches shoulder. Determine location of elbow in relation to midline. Elbow does not reach midline = 4.

Heel to ear.

With infant supine and pelvis flat on firm surface, pull foot as far as possible toward ear on same side. Measure distance of foot from ear and degree of knee flexion (same as popliteal angle). Knees flexed with popliteal angle of <90 degrees = 4.

Data from Hockenberry MJ, Wilson D: Wong’s essentials of pediatric nursing, ed 8, St. Louis, 2009, Mosby.

FIGURE 2-1 New Ballard Score. (From Ballard JL, Khoury JC, Wedig K et al: New Ballard Score, expanded to include extremely premature infants, J Pediatr 119(3):418, 1991.)

The Apgar scoring system (Table 2-1) reflects the transition of the neonate to extrauterine life. The Apgar assessment performed at 1 minute and again at 5 minutes after birth reflects the heart rate, observation of respiratory effort, muscle tone, reflex irritability, and color of the newborn (Table 2-2). The Apgar score is not predictive of long-term perinatal outcomes or neurological status, but remains the standard for assessing viability of the newborn immediately after birth. The Physiscore is a physiological assessment score for preterm infants based on electronic non-invasive measurements monitored in the first 3 hours of life. It may provide higher accuracy of morbidity than the Apgar score.²

TABLE 2-1

Apgar Scoring System

Data from Apgar V: Evaluation of the newborn infant, second report, JAMA 168(15):1985-1988, 1958.

TABLE 2-2

Interpretation of Apgar Scores

Total Score	Assessment
0-2	Severe asphyxia
3-4	Moderate asphyxia
5-7	Mild asphyxia
8-10	No asphyxia

Term infants

Term infants are born between the 38th and 41st weeks of gestation and normally lose about 5% to 10% of their birth weight in the first 72 hours after birth. The average weight loss is 5% to 7% over 3 to 4 days. Postterm infants are born at 42 weeks of gestation and represent about 10% of the newborn population. Postterm infants have an increased incidence of fetal distress and perinatal asphyxia, often due to increased weight gain before delivery. In term infants, a weight loss of >10% may indicate a poor feeding pattern or a more serious postnatal condition and requires thorough investigation and close follow-up. For the infant who is breastfed, observation of feeding and latch to the nipple is particularly important for the breastfed infant with a >7% to >10% weight loss. By 2 weeks of age, term infants have normally regained their birth weight.

Evidence-Based Practice Tip

The maximum point of weight loss can occur any day during the first week postpartum. Weight loss of greater than 10% should be evaluated and the infant should be monitored for intake.³

Preterm infants

An infant is considered preterm when born before the end of the 37th week. The weight and gestational age of the infant together predict the relative risk of mortality. During the first year of life, premature infants tend to grow more slowly than term infants even when using the growth curve standard for corrected age (see Appendix A). Health care providers should use the adjusted age standard when plotting the growth of the preterm infant until the infant is 2½ years old. At this point, the difference is no longer statistically significant.

Low birth weight infants

Low birth weight (LBW) infants are those infants born weighing <2500 g. Very low birth weight (VLBW) infants are those infants who weigh <1500 g at birth, and infants weighing ≤1000 g are considered extremely low birth weight (ELBW). There has been an increase in the number of VLBW infants due mainly to the increase in prematurely born multiple gestations. However, race and ethnicity, maternal age, maternal health and nutrition, substance abuse during pregnancy, environmental toxins, and access to prenatal care all contribute to the risk of LBW infants. In 2010, the prevalence of LBW infants in the United States was 8.2%, with the highest prevalence among African-Americans.⁴ Box 2-2 presents maternal risk factors for LBW and VLBW infants.

BOX 2-2

Maternal Risk Factors for Low Birth Weight and Very Low Birth Weight Infants

Maternal risks

• Maternal age

• Race and ethnicity

• Maternal health and nutrition

• Environmental toxins or occupational chemical toxins

• Access to prenatal care

Maternal substance abuse

• Alcoholism

• Tobacco use

• Illicit drug use

• Over-the-counter drug use

Data from Malloy MH: Size for gestational age at birth: Impact on risk for sudden infant death and other causes of death, USA 2002, Arch Dis Child Fetal Neonatal Ed, 92(6):F473-478, 2007.

Measurement

Head circumference

Measurement of head circumference is a routine part of growth assessment in the first 2 years of life. Accurate measurement of the head is taken with the measuring tape around the head placed at the point of greatest circumference from the occipital protuberance above the base of the skull to the midforehead or point of greatest bossing of the frontal bone (Figure 2-2). The head circumference measurement is then plotted on the growth curve specific for sex and age at each well-child visit to determine if the growth pattern is normal. If the initial head measurement is plotted on the growth chart and indicates a concerning pattern of growth, it is important to remeasure the head to ensure accuracy of head size. A head circumference that plots 1 to 2 SD above height and weight on the growth curve or >95th percentile or <5th percentile for age should be evaluated. Microcephaly may be indicative of an SGA infant, IUGR, or premature closure of the cranial sutures, termed craniosynostosis, which requires immediate referral. Macrocephaly, a large head in proportion to the body, may indicate increased intracranial pressure or may be a familial variant. Consistent and accurate assessment of the head circumference is a critical part of the assessment of normal growth and development.