Every newborn is classified three ways: by gestational age, by birth weight, and by weight for gestational age (intrauterine growth). Each classification predicts a different set of risks, so the nurse assesses all three in the first hours of life.

Classification by gestational age (completed weeks)

Classification by birth weight (regardless of gestational age)

Classification by growth (plotted on a growth chart)

• Small for gestational age (SGA): weight below the 10th percentile for gestational age. May reflect intrauterine growth restriction (placental insufficiency, maternal hypertension or smoking, infection, chromosomal disorders).
• Appropriate for gestational age (AGA): 10th to 90th percentile.
• Large for gestational age (LGA): above the 90th percentile. Most often linked to maternal diabetes or obesity.

The categories are independent. For example, a 34-week infant weighing 2,100 g is preterm, low birth weight, and AGA at the same time.

Why preterm infants are high risk: organ systems are structurally and functionally immature. Surfactant production is insufficient (respiratory distress syndrome), the brainstem respiratory center is immature (apnea), brown fat and subcutaneous fat are scant (cold stress), glycogen stores are low (hypoglycemia), the liver conjugates bilirubin poorly (jaundice), the immune system is immature (sepsis), the germinal matrix is fragile (intraventricular hemorrhage), the retina is incompletely vascularized (retinopathy of prematurity), and the gut is vulnerable (necrotizing enterocolitis). Late preterm infants often look mature but share many of these risks, especially feeding problems, jaundice, hypoglycemia, and temperature instability.

Physical maturity — preterm vs. term vs. post-term

Post-term infants may also look wasted (loss of subcutaneous fat) and have meconium-stained skin, nails, and cord.

Neuromuscular maturity — maturity moves from extension and hypotonia (preterm) to flexion and tone (term).

• Posture: preterm infant lies with limbs extended; term infant holds all limbs flexed.
• Square window (wrist flexion): preterm has a wide angle; the term infant's hand flexes flat against the forearm.
• Arm recoil: slow or absent in preterm; brisk in term.
• Popliteal angle: large (knee extends easily) in preterm; small in term.
• Scarf sign: in preterm the elbow crosses the midline easily; in term it does not reach the midline.
• Heel to ear: the preterm heel reaches the ear with little resistance.

Tool: the New Ballard Score combines 6 physical and 6 neuromuscular signs to estimate gestational age (it extends down to about 20 weeks). The Apgar score assesses transition at birth, not maturity; developmental tools such as the Denver II and Brazelton scale are not used to date gestation.

Ongoing assessment of the preterm infant: temperature, respiratory rate and effort, apnea and bradycardia events, SpO₂, blood glucose, feeding tolerance, skin integrity, jaundice, daily weight, head circumference, and length weekly.

Before and at birth

• Maternal antenatal corticosteroids (betamethasone or dexamethasone) when preterm birth is expected before 34 weeks, and in selected cases up to 36 6/7 weeks (generally not given to mothers with pregestational diabetes), to accelerate lung maturity. Maternal effects: transient hyperglycemia (monitor glucose in mothers with diabetes); late-preterm courses increase neonatal hypoglycemia.
• Maternal magnesium sulfate for fetal neuroprotection when birth before 32 weeks is expected (reduces cerebral palsy). Monitor the mother for toxicity (loss of deep tendon reflexes, respiratory depression, low urine output; calcium gluconate is the antidote); the newborn may be hypotonic or have depressed respirations.
• Delayed cord clamping (at least 30–60 seconds) for vigorous term and preterm infants improves blood volume and reduces transfusion need.
• Resuscitation team present for preterm births.

Thermal protection

• For infants born before about 32 weeks, place in a polyethylene wrap or bag without drying the body, with a hat, under a radiant warmer, in a warm delivery room.
• Target axillary temperature 36.5–37.5 °C (97.7–99.5 °F). Cold stress raises oxygen consumption and glucose use and can lead to hypoglycemia, metabolic acidosis, and respiratory distress.

Nutrition

• Human milk is preferred (mother's own milk; donor milk if unavailable). Very preterm infants need a human milk fortifier for protein, calories, and minerals.
• Parenteral nutrition in the smallest infants, with early small-volume ("trophic") enteral feeds advanced cautiously.
• Gavage feeding until the suck–swallow–breathe pattern is coordinated (usually around 32–34 weeks); then cue-based oral feeding.

Routine newborn medications (doses per unit protocol and weight)

• Vitamin K (phytonadione) IM — prevents vitamin K deficiency bleeding; a lower dose is used for small preterm infants.
• Erythromycin eye ointment — prophylaxis against gonococcal ophthalmia.
• Hepatitis B vaccine and hepatitis B immune globulin (HBIG) — timing depends on maternal HBsAg status and birth weight:
  • Mother HBsAg-positive: vaccine + HBIG within 12 hours, regardless of weight
  • Mother's status unknown: vaccine within 12 hours; add HBIG within 12 hours if the infant weighs under 2,000 g; if 2,000 g or more, give HBIG within 7 days only if the mother tests positive
  • Mother HBsAg-negative: infants of 2,000 g or more receive the universal birth dose within 24 hours; infants under 2,000 g receive the first dose at 1 month of age or hospital discharge, whichever comes first (US federal vaccine policy has been in litigation since 2026 — check the current CDC schedule)
  • A dose given at birth to an infant under 2,000 g does not count toward the series
• Immunizations are otherwise given by chronological age, not corrected age, in medically stable preterm infants.

Listed in priority order.

1. Airway and breathing
   • Monitor respiratory rate, work of breathing (retractions, grunting, nasal flaring), SpO₂, and apnea/bradycardia alarms continuously
   • Position with the neck neutral or slightly extended ("sniffing"); avoid neck flexion, which obstructs the soft airway
2. Thermoregulation
   • Radiant warmer or incubator in servo-control mode; keep portholes closed; warm hands, linens, and equipment
   • Skin-to-skin (kangaroo) care when stable — supports temperature, breastfeeding, and bonding
   • Recognize signs of cold stress: cool skin, mottling, lethargy, poor feeding, apnea, hypoglycemia
3. Glucose and fluids — screen glucose per protocol; strict intake and output; weigh daily on the same scale
4. Infection prevention — rigorous hand hygiene, central line care bundles, limit exposure to ill visitors
5. Skin protection — minimal adhesive, silicone-based products, gentle removal; avoid alcohol and povidone-iodine residue on fragile skin
6. Developmental care
   • Cluster care; dim lights; reduce noise; cover the incubator
   • Positioning in flexion with boundaries ("nesting"); facilitated tucking
   • Non-nutritive sucking during gavage feeds
7. Pain management — use a neonatal pain scale; non-drug measures such as oral sucrose, facilitated tucking, and skin-to-skin care for minor procedures
8. Family support — open visiting, participation in care, breast milk expression support, preparation for discharge

Discharge readiness (typical criteria): stable temperature in an open crib, oral feeding with steady weight gain, no recent significant apnea, completed screening (hearing, newborn screening, eye examination as indicated), and a car seat tolerance screen for infants born before 37 weeks.

• Growth and development are judged by corrected age (chronological age minus weeks born early) until about 2 years
• Vaccines follow the chronological age schedule
• Place the baby on the back to sleep on a firm, flat surface without pillows or bumpers, once off monitoring — do not continue the prone positioning used in the NICU
• Feeding: watch hunger cues, burp often, and count wet diapers
• Keep the baby warm but not overheated; avoid crowds and sick contacts during the first months
• Hand hygiene for everyone; no smoking or vaping near the infant
• Report: poor feeding, breathing pauses or color change, fever or low temperature, increasing jaundice, lethargy
• Keep follow-up appointments for eye examinations, hearing, and developmental screening

Red flags: temperature below 36.5 °C (97.7 °F), apnea with bradycardia or desaturation, increasing oxygen need, abdominal distension or bloody stools, lethargy, bulging fontanel, seizures.

• Preterm = before 37 weeks; late preterm = 34 0/7–36 6/7; post-term = 42 weeks or more
• LBW < 2,500 g, VLBW < 1,500 g, ELBW < 1,000 g; SGA < 10th percentile, LGA > 90th percentile
• Weight class and gestational-age class are separate — an infant can be preterm and AGA and LBW at once
• Preterm: translucent skin, abundant lanugo, few plantar creases, soft ears, extended posture, scarf sign crosses midline
• Post-term: dry peeling skin, long nails, meconium staining → risk of meconium aspiration
• New Ballard Score estimates gestational age; Apgar does not
• Thermoregulation is a top priority after airway; wrap infants under about 32 weeks in plastic without drying
• LGA/infant of diabetic mother and SGA → hypoglycemia screening
• Development by corrected age; immunizations by chronological age
• Car seat tolerance screen before discharge for infants born before 37 weeks