Neonatology

01 Neonatal Physiology & Transition

The transition from intrauterine to extrauterine life is the most complex physiologic adaptation that occurs in human biology. Within seconds to minutes of birth, the neonate must establish independent gas exchange, redirect circulatory pathways, maintain thermoregulation, and achieve metabolic homeostasis. Understanding fetal circulation and its postnatal transition is foundational to all neonatal care.

Fetal Circulation

Fetal circulation is a parallel circuit (unlike the postnatal series circuit) optimized to deliver the most oxygenated blood to the brain and myocardium. Three unique shunts characterize fetal hemodynamics:

In utero, the placenta is the organ of gas exchange. The umbilical vein carries oxygenated blood (PaO₂ ~30–35 mmHg) from the placenta to the fetus. Approximately 50% passes through the ductus venosus to the IVC; the remainder perfuses the hepatic sinusoids. In the IVC, this relatively oxygenated blood preferentially streams across the foramen ovale into the left atrium, then to the left ventricle and ascending aorta — supplying the coronary arteries and brain with the most oxygenated blood available. Deoxygenated blood returning via the SVC flows into the right ventricle and out the pulmonary artery, where 90% is diverted through the ductus arteriosus to the descending aorta (and back to the placenta via the umbilical arteries).

Transitional Circulation — The First Breath

Birth triggers a cascade of events that convert the parallel fetal circuit into the adult series circuit:

• Cord clamping → removes low-resistance placental circuit → systemic vascular resistance (SVR) rises → aortic pressure increases
• First breath → lung expansion → alveolar fluid clearance (driven by sodium channel activation, especially ENaC) → pulmonary vascular resistance (PVR) drops dramatically
• Rising PaO₂ causes pulmonary vasodilation (via nitric oxide and prostacyclin) and ductal constriction
• Decreased PVR → increased pulmonary blood flow → increased LA return → LA pressure exceeds RA pressure → foramen ovale closes
• Rising O₂ + falling prostaglandin E₂ and I₂ → ductus arteriosus constricts

Thermoregulation

Neonates, especially preterm infants, are extremely vulnerable to hypothermia due to:

• Large surface area-to-body mass ratio
• Thin skin with minimal subcutaneous fat insulation
• Inability to shiver (neonates rely on non-shivering thermogenesis)
• Wet skin at delivery (evaporative losses)

Brown adipose tissue (BAT) is the primary source of heat production in neonates. Located between the scapulae, around the kidneys, and along the great vessels, BAT contains high concentrations of mitochondria with uncoupling protein 1 (UCP-1, thermogenin) that dissipates the proton gradient as heat rather than ATP. BAT thermogenesis is triggered by norepinephrine via β₃-adrenergic receptors. Hypothermia increases oxygen consumption and can lead to metabolic acidosis, hypoglycemia, and increased mortality — maintaining a neutral thermal environment (NTE, axillary temperature 36.5–37.5°C) is a core principle of neonatal care.

Glucose Homeostasis

The fetus receives a continuous glucose supply via the placenta. At birth, this supply is abruptly terminated, and the neonate must rapidly activate glycogenolysis and gluconeogenesis. Term infants normally experience a physiologic nadir in blood glucose (as low as 30 mg/dL) at 1–2 hours of life, which rises spontaneously by 3–4 hours with feeding. Preterm infants, SGA infants, and infants of diabetic mothers (IDM) are at high risk for hypoglycemia due to limited glycogen stores, increased metabolic demands, and (in IDM) hyperinsulinism from fetal exposure to maternal hyperglycemia.

02 APGAR Score & Neonatal Assessment

The APGAR score, introduced by Virginia Apgar in 1952, is the most widely used rapid assessment tool for neonatal transition. It is performed at 1 and 5 minutes of life (and at 5-minute intervals thereafter if the score remains <7). The APGAR does not determine the need for resuscitation — resuscitation should begin before the 1-minute score is assigned.

APGAR Score Components

New Ballard Score — Gestational Age Assessment

The New Ballard Score (NBS) estimates gestational age from 20 to 44 weeks based on six neuromuscular and six physical maturity criteria. It is accurate to ±2 weeks and is most reliable when performed within 48 hours of birth (up to 96 hours for premature infants). Each criterion is scored from −1 to 5 (neuromuscular) or −1 to 4 (physical); the total is mapped to gestational age.

Growth Classification

Birth weight is classified relative to gestational age using population-based growth curves (Fenton or Olsen charts):

• Small for gestational age (SGA): Birth weight <10th percentile for gestational age
• Appropriate for gestational age (AGA): Birth weight 10th–90th percentile
• Large for gestational age (LGA): Birth weight >90th percentile

SGA infants are at risk for hypoglycemia, polycythemia, hypothermia, and may have underlying IUGR (intrauterine growth restriction) from placental insufficiency, maternal hypertension, or congenital infection. LGA infants are commonly seen in maternal diabetes and are at risk for birth trauma (shoulder dystocia, brachial plexus injury), hypoglycemia, and polycythemia.

03 Terminology & Abbreviations

Neonatology uses a specialized vocabulary for gestational age classification, birth weight categories, and clinical conditions. Mastery of these terms is essential for documentation, communication, and interpreting the neonatal literature.

04 NRP Algorithm

Approximately 10% of newborns require some assistance to begin breathing, and about 1% require extensive resuscitation. The Neonatal Resuscitation Program (NRP), updated in the 8th edition (2020), provides an evidence-based, algorithmic approach. Every delivery should have at least one person skilled in NRP present whose sole responsibility is the newborn.

Initial Assessment (Birth)

Three rapid questions at birth determine the initial approach:

• Term gestation?
• Good muscle tone?
• Breathing or crying?

If yes to all three → routine care: skin-to-skin, dry, clear airway as needed, ongoing assessment. If no to any → move to the radiant warmer and begin initial steps.

Initial Steps (within 30 seconds)

Warm (radiant warmer, dry, remove wet linen, polyethylene wrap for <32 weeks), position (sniffing position, shoulder roll if needed), clear airway (gentle suctioning only if secretions obstruct; mouth before nose), dry, and stimulate (flick soles, rub back).

Positive Pressure Ventilation (PPV)

If HR <100 bpm or apneic/gasping after initial steps → begin PPV at 40–60 breaths/min using a T-piece resuscitator or self-inflating bag with a correctly sized mask (covers mouth and nose but not eyes). Initial PIP: 20–25 cm H₂O (up to 30–40 for the first few breaths if needed to establish FRC). Initial FiO₂: 21% for ≥35 weeks; 21–30% for <35 weeks. Titrate by pulse oximetry.

MR SOPA — Corrective Steps for Ineffective PPV

Chest Compressions

If HR <60 bpm despite 30 seconds of effective PPV (with adequate chest rise) → begin chest compressions. Use the two-thumb encircling technique (preferred): compress the lower third of the sternum to a depth of one-third the AP diameter. Ratio: 3 compressions : 1 ventilation (3:1), delivering 90 compressions + 30 ventilations = 120 events per minute. Increase FiO₂ to 100% when compressions are initiated.

Epinephrine & Vascular Access

If HR remains <60 bpm despite effective PPV + compressions for 60 seconds → administer epinephrine:

• IV (UVC preferred): 0.01–0.03 mg/kg (0.1–0.3 mL/kg of 1:10,000) — may repeat every 3–5 minutes
• Endotracheal: 0.05–0.1 mg/kg (0.5–1 mL/kg of 1:10,000) — only while IV access is being established

An umbilical venous catheter (UVC) is the preferred emergency vascular access in the delivery room. Insert through the umbilical vein (thin-walled, single vessel) to a depth where blood can be freely aspirated (typically 2–4 cm in a term infant — just past the abdominal wall).

Meconium-Stained Amniotic Fluid

The 2020 NRP no longer recommends routine intubation and tracheal suctioning for non-vigorous infants born through meconium-stained fluid. Instead, follow the standard NRP algorithm: provide initial steps and PPV if needed. Intubation and tracheal suctioning should be considered only if the airway appears obstructed despite proper PPV technique.

05 Delivery Room Stabilization

Delayed Cord Clamping

Delayed cord clamping (DCC) is recommended for all vigorous newborns who do not require immediate resuscitation:

• Term infants: Delay clamping for at least 30–60 seconds; improves iron stores, reduces iron deficiency anemia at 3–6 months
• Preterm infants: Delay clamping for at least 30 seconds; reduces IVH, NEC, need for transfusion, and improves transitional circulation

If DCC is not possible (non-vigorous infant, placental abruption), umbilical cord milking (stroking the cord 3–4 times toward the infant over 2 seconds) is an alternative, though evidence is less robust and it is not recommended for infants <28 weeks due to a possible association with increased IVH.

Temperature Management

Target admission temperature: 36.5–37.5°C. Hypothermia on NICU admission is an independent predictor of mortality and morbidity in preterm infants. Strategies by gestational age:

Target SpO₂ by Minute of Life

Healthy term newborns do not achieve SpO₂ >90% until approximately 10 minutes after birth. The NRP provides target preductal SpO₂ ranges (right hand):

Initial FiO₂ Recommendations

• ≥35 weeks GA: Start at 21% (room air); titrate by pulse oximetry
• <35 weeks GA: Start at 21–30%; titrate to target SpO₂ ranges above
• Avoid hyperoxia (>95%) in preterm infants — increases ROP risk and oxidative stress

06 Perinatal Asphyxia & HIE

Hypoxic-ischemic encephalopathy (HIE) results from impaired cerebral blood flow and oxygen delivery around the time of birth, leading to a cascade of excitotoxicity, oxidative stress, inflammation, and apoptosis. It occurs in 1–3 per 1,000 term live births and remains a leading cause of neonatal death and long-term neurodisability.

Sarnat Staging of HIE

Therapeutic Hypothermia

Therapeutic hypothermia (TH) is the only proven neuroprotective intervention for moderate-to-severe HIE. It reduces death and major neurodisability by approximately 25%.

Amplitude-Integrated EEG (aEEG)

aEEG provides continuous bedside monitoring of cerebral electrical activity. Background patterns classified as: continuous normal voltage (CNV, best prognosis), discontinuous normal voltage (DNV), burst suppression, continuous low voltage, and flat trace (worst prognosis). aEEG within 6 hours is used to help determine eligibility for TH and predict outcomes. Seizures appear as sudden rises in both upper and lower margins.

07 Respiratory Distress Syndrome

Respiratory distress syndrome (RDS), formerly known as hyaline membrane disease, is caused by deficiency of pulmonary surfactant, a complex mixture of phospholipids (primarily dipalmitoylphosphatidylcholine/DPPC) and surfactant proteins (SP-A, SP-B, SP-C, SP-D) produced by type II pneumocytes. Surfactant reduces alveolar surface tension, prevents end-expiratory atelectasis, and improves lung compliance. RDS is the leading cause of respiratory failure in premature infants.

Risk Factors

• Prematurity — the primary risk factor; surfactant production begins at ~24 weeks and is adequate by ~35 weeks
• Maternal diabetes (insulin inhibits surfactant production)
• Male sex (androgens delay surfactant maturation)
• Cesarean delivery without labor (lack of catecholamine surge)
• Perinatal asphyxia, hypothermia
• Multiple gestation (second twin)

Clinical Features & Diagnosis

Onset within minutes to hours of birth: tachypnea, nasal flaring, intercostal/subcostal retractions, expiratory grunting (attempts to maintain FRC by adducting vocal cords), cyanosis. Progressive worsening over 48–72 hours without treatment, then gradual improvement as endogenous surfactant production increases.

CXR findings: Diffuse, bilateral, reticulogranular (“ground-glass”) opacities with air bronchograms, decreased lung volumes. Severe cases may show complete “white-out” with indistinguishable cardiac silhouette.

Management

Prevention

Antenatal corticosteroids are the most effective intervention for preventing RDS: betamethasone 12 mg IM × 2 doses 24 hours apart (or dexamethasone 6 mg IM × 4 doses 12 hours apart) given to mothers at 24–34 weeks gestation with threatened preterm delivery. Reduces RDS incidence by ~50%, IVH, NEC, and neonatal mortality.

08 Transient Tachypnea & Meconium Aspiration

Transient Tachypnea of the Newborn (TTN)

TTN (“wet lung”) is the most common cause of respiratory distress in term and late preterm newborns, caused by delayed clearance of fetal lung fluid. Normally, labor triggers catecholamine-mediated activation of epithelial sodium channels (ENaC) that reabsorb lung fluid. Cesarean delivery without labor bypasses this mechanism.

• Risk factors: Elective cesarean without labor, precipitous delivery, maternal diabetes, maternal sedation, late preterm birth
• Presentation: Tachypnea (RR 60–120), mild retractions, occasional grunting within the first 2 hours; usually self-resolving within 24–72 hours
• CXR: Perihilar streaking, fluid in fissures, hyperinflation, flattened diaphragms
• Management: Supportive — supplemental O₂ (rarely >40%), CPAP if needed; NPO until RR <60–80; self-resolving

Meconium Aspiration Syndrome (MAS)

Meconium-stained amniotic fluid (MSAF) occurs in 8–15% of deliveries, but MAS develops in only 2–5% of those. Meconium passage is a sign of fetal maturity (rarely occurs before 34 weeks) or fetal distress (hypoxia triggers vagal stimulation → passage of meconium, followed by gasping → aspiration).

Pathophysiology: Meconium causes (1) mechanical airway obstruction with ball-valve effect → air trapping and pneumothorax, (2) chemical pneumonitis from bile acids and enzymes, (3) surfactant inactivation, and (4) pulmonary vasoconstriction → PPHN.

Persistent Pulmonary Hypertension of the Newborn (PPHN)

PPHN occurs when PVR remains elevated after birth, causing right-to-left shunting through the foramen ovale and ductus arteriosus. Etiologies: MAS (most common), RDS, pneumonia, CDH, idiopathic. Presents with labile hypoxemia, preductal-postductal SpO₂ difference >5–10%, and poor response to supplemental O₂.

• Inhaled nitric oxide (iNO): Selective pulmonary vasodilator; dose 20 ppm; reduces need for ECMO; wean by 5 ppm decrements when FiO₂ <60%; do not discontinue abruptly (rebound PHN)
• Sildenafil: PDE-5 inhibitor; 0.5–2 mg/kg PO q6–8h; used as adjunct or when iNO is unavailable
• Milrinone: PDE-3 inhibitor/inodilator; improves RV function; load 50 mcg/kg then 0.33–0.99 mcg/kg/min
• ECMO: Last resort for refractory PPHN; criteria: oxygenation index (OI) >40, ≥34 weeks GA, weight >2 kg

09 Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy, resulting from arrested alveolar and vascular development in the immature lung, compounded by inflammation from mechanical ventilation, oxygen toxicity, and infection.

Definition & Grading

The 2001 NICHD definition classifies BPD in infants born <32 weeks based on respiratory support at 36 weeks PMA (or discharge, whichever comes first):

The Jensen 2019 evidence-based definition simplifies grading based solely on the mode of respiratory support at 36 weeks PMA, regardless of FiO₂:

Prevention

• Caffeine — the CAP trial demonstrated a significant reduction in BPD; start within 24 hours of birth
• Vitamin A — 5,000 IU IM 3 times/week for 4 weeks; modest BPD reduction in ELBW infants
• Gentle ventilation — target lowest effective pressures and tidal volumes (4–6 mL/kg); permissive hypercapnia (PaCO₂ 45–55 mmHg)
• Early CPAP — avoid intubation when possible; CPAP from delivery room
• Judicious oxygen use — target SpO₂ 91–95% in preterm infants

Management of Established BPD

• Diuretics: Furosemide 1–2 mg/kg/day or chlorothiazide 10–20 mg/kg/dose BID + spironolactone 1–2 mg/kg/day; improves lung compliance but no proven mortality benefit
• Inhaled corticosteroids: Budesonide nebulized; may reduce need for systemic steroids
• Postnatal dexamethasone: Facilitates extubation in ventilator-dependent infants; DART protocol (0.15 mg/kg/day tapered over 10 days); use cautiously due to concerns about neurodevelopmental adverse effects; reserve for infants unable to wean from mechanical ventilation
• Nutritional optimization: Caloric needs increased (120–150 kcal/kg/day); fortified breast milk or 24–27 kcal/oz formula
• Discharge on home O₂: If SpO₂ <92% in room air; with home pulse oximetry; wean as tolerated at follow-up

10 Neonatal Ventilation

Respiratory support in the NICU spans a spectrum from non-invasive strategies (CPAP, HFNC) to conventional mechanical ventilation and high-frequency oscillatory/jet ventilation. The principle of lung-protective ventilation — using the minimum support necessary to maintain acceptable gas exchange — is paramount to reducing ventilator-induced lung injury and BPD.

Non-Invasive Respiratory Support

Conventional Mechanical Ventilation

When non-invasive support fails (persistent apnea, rising FiO₂, worsening acidosis), intubation and mechanical ventilation are indicated.

High-Frequency Ventilation

Weaning Strategies

Wean FiO₂ first to <30–40%, then reduce PIP/MAP as tolerated. Target permissive hypercapnia (PaCO₂ 45–55 mmHg, pH >7.22) to minimize volutrauma and allow lower ventilator settings. Extubation criteria: low ventilator settings (MAP <8, FiO₂ <30%, rate <15–20), adequate spontaneous respiratory effort, caffeine on board. Extubate to CPAP or NIPPV.

11 Neonatal Sepsis

Neonatal sepsis is a clinical syndrome of systemic infection in the first 28 days of life. It is a leading cause of neonatal morbidity and mortality, particularly in preterm infants. Classification by timing of onset has critical implications for microbiology, evaluation, and empiric therapy.

Early-Onset Sepsis (EOS) vs. Late-Onset Sepsis (LOS)

GBS Prophylaxis

Universal screening at 36 0/7–37 6/7 weeks with rectovaginal culture. Intrapartum antibiotic prophylaxis (IAP) with penicillin G (5 million units IV loading, then 2.5–3 million q4h) or ampicillin (2 g IV loading, then 1 g q4h) is given to GBS-positive mothers, those with GBS bacteriuria in current pregnancy, or prior infant with GBS disease. Adequate prophylaxis = ≥4 hours before delivery.

Evaluation & Workup

• Blood culture: Minimum 1 mL in a single aerobic bottle (sensitivity ~80%); the gold standard
• CBC with differential: WBC <5,000 or >30,000, I:T ratio >0.2 (immature:total neutrophils), thrombocytopenia, neutropenia
• CRP: Low sensitivity at onset; serial CRP at 24–48 hours has high NPV (>99%); useful for guiding antibiotic discontinuation
• Procalcitonin: Rises earlier than CRP; physiologic surge in first 24–48 hours limits utility in EOS
• Lumbar puncture: Indicated if blood culture positive, clinical signs of meningitis, or infant deteriorating; CSF: WBC >20–30 cells, protein >150 mg/dL (term) or >200 mg/dL (preterm), glucose <60% of serum

Duration of Therapy

• Bacteremia without focus: 7–10 days
• Meningitis (GBS): 14–21 days
• Gram-negative meningitis: 21 days (or 14 days after first sterile CSF culture)
• Negative cultures, well infant: Discontinue empiric antibiotics at 36–48 hours

12 TORCH Infections

TORCH is a mnemonic for congenital infections that share overlapping clinical features: intrauterine growth restriction, hepatosplenomegaly, jaundice, thrombocytopenia, rash, and central nervous system involvement. Each infection has unique characteristics that guide diagnosis and treatment.

Toxoplasmosis

Rubella

Cytomegalovirus (CMV)

Herpes Simplex Virus (HSV)

Syphilis

Zika Virus

Congenital Zika syndrome: severe microcephaly with partially collapsed skull, subcortical calcifications, macular scarring, congenital contractures (arthrogryposis), and marked neurological impairment. Transmitted by Aedes mosquitoes or sexually. Diagnosis: Zika IgM, RT-PCR in maternal/infant serum and urine. No specific treatment; supportive care.

13 Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common life-threatening gastrointestinal emergency in neonates, affecting 5–10% of VLBW infants, with mortality of 20–30% (up to 50% in those requiring surgery). It is characterized by intestinal inflammation, mucosal necrosis, and bacterial invasion of the bowel wall.

Pathophysiology & Risk Factors

NEC results from a complex interplay of intestinal immaturity, abnormal bacterial colonization, ischemia-reperfusion injury, and inflammatory cascade activation. The terminal ileum and ascending colon are most commonly affected.

• Prematurity — the single greatest risk factor (90% of NEC occurs in preterm infants)
• Formula feeding — breast milk is strongly protective (up to 6–10× lower risk)
• Abnormal intestinal flora / dysbiosis
• Intestinal ischemia (PDA with diastolic steal, CHD, polycythemia)
• Rapid advancement of enteral feeds
• Prolonged empiric antibiotics (alters microbiome)

Modified Bell Staging Criteria

Surgical Indications

• Absolute: Pneumoperitoneum (intestinal perforation)
• Relative: Fixed dilated loop on serial radiographs, portal venous gas, clinical deterioration despite maximal medical therapy, abdominal wall erythema/induration, positive paracentesis (bile-stained or bacteria on Gram stain)

Prevention

Human breast milk is the most effective preventive measure. The AAP recommends exclusive breast milk for all preterm infants; donor human milk if mother’s own milk is unavailable. Standardized feeding protocols (slow, consistent advancement at 20–30 mL/kg/day), avoidance of prolonged empiric antibiotics, and probiotics (evidence supports Lactobacillus and Bifidobacterium species, though specific products and dosing remain debated) all reduce NEC incidence.

14 Neonatal Hyperbilirubinemia

Jaundice is visible in ~60% of term and ~80% of preterm newborns in the first week of life. Most jaundice is benign (physiologic), but unchecked unconjugated hyperbilirubinemia can cause bilirubin encephalopathy and kernicterus, a devastating and preventable condition.

Bilirubin Metabolism in the Neonate

Neonates produce bilirubin at twice the adult rate (higher RBC mass, shorter RBC lifespan of 60–90 days vs. 120 days) and have immature hepatic conjugation (low UDP-glucuronosyltransferase/UGT1A1 activity). Unconjugated (indirect) bilirubin is lipid-soluble and crosses the blood-brain barrier; conjugated (direct) bilirubin is water-soluble and does not cause neurotoxicity.

Physiologic vs. Pathologic Jaundice

Bhutani Nomogram

The Bhutani hour-specific nomogram plots total serum bilirubin (TSB) against the infant’s age in hours and classifies risk as: low risk (<40th percentile), low-intermediate (40th–75th), high-intermediate (75th–95th), and high risk (>95th percentile). Risk zone at discharge guides follow-up timing and need for repeat TSB.

Phototherapy Thresholds (AAP 2022 Guidelines)

*Risk factors (neurotoxicity risk): isoimmune hemolytic disease, G6PD deficiency, asphyxia, sepsis, acidosis, albumin <3.0 g/dL. Values in mg/dL. Thresholds are approximate; always refer to gestational age and hour-specific AAP charts.

Exchange Transfusion

Indicated when TSB rises to exchange transfusion threshold (generally 2–5 mg/dL above phototherapy threshold depending on age and risk factors) or if signs of acute bilirubin encephalopathy develop. Double-volume exchange (160–180 mL/kg) removes ~85% of circulating bilirubin and antibody-coated RBCs. Risks: electrolyte disturbances, thrombocytopenia, infection, NEC, portal vein thrombosis.

Bilirubin Encephalopathy & Kernicterus

• Acute bilirubin encephalopathy: Early — lethargy, hypotonia, poor feeding; Intermediate — hypertonia (opisthotonos, retrocollis), high-pitched cry, fever; Advanced — pronounced opisthotonos, apnea, seizures, coma
• Chronic bilirubin encephalopathy (kernicterus): Tetrad of choreoathetoid cerebral palsy, upward gaze palsy, sensorineural hearing loss, and dental enamel hypoplasia

Breastfeeding vs. Breast Milk Jaundice

15 Neonatal Hypoglycemia

Neonatal hypoglycemia is one of the most common metabolic problems in the nursery. While a precise definition remains debated, the AAP Committee on Fetus and Newborn uses an operational threshold of <45 mg/dL (2.5 mmol/L) as the level below which intervention is recommended in symptomatic and at-risk neonates.

At-Risk Populations

Clinical Features

Symptoms are non-specific: jitteriness, tremors, poor feeding, lethargy, hypotonia, apnea, seizures, cyanosis, hypothermia. Many hypoglycemic neonates are asymptomatic, underscoring the importance of screening at-risk infants.

Management Algorithm

Persistent Hypoglycemia Workup

If hypoglycemia persists beyond 48–72 hours or requires GIR >12 mg/kg/min, obtain a critical sample during hypoglycemia (glucose <50 mg/dL):

• Insulin — elevated insulin with low glucose = hyperinsulinism (insulin:glucose ratio >0.3)
• Cortisol — low cortisol = adrenal insufficiency
• Growth hormone — low GH = GH deficiency
• Free fatty acids & beta-hydroxybutyrate — suppressed in hyperinsulinism (insulin inhibits lipolysis and ketogenesis)
• Lactate, ammonia, acylcarnitine profile, urine organic acids — fatty acid oxidation defects, organic acidemias, glycogen storage diseases

16 Fluid, Electrolytes & Nutrition

Daily Fluid Requirements

Neonatal fluid management is guided by gestational age, postnatal age, body weight changes, urine output, and serum sodium. Insensible water loss (IWL) is highest in the most premature infants due to thin, permeable skin and high surface area-to-volume ratio.

Expect a physiologic weight loss of 5–10% in term and 10–15% in ELBW infants over the first week, primarily from extracellular fluid contraction.

Electrolyte Requirements

Total Parenteral Nutrition (TPN)

Initiate TPN within the first hours of life for preterm infants unable to tolerate full enteral feeds:

• Dextrose: Start D10W (GIR ~4–6 mg/kg/min); advance to D12.5–D15 as needed (max GIR ~11–12 mg/kg/min via peripheral IV)
• Amino acids: Start 2–3 g/kg/day on DOL 1; advance to 3.5–4 g/kg/day by DOL 3–5
• Lipids (intralipid 20%): Start 1–2 g/kg/day on DOL 1; advance to 3 g/kg/day; monitor triglycerides (keep <200–250 mg/dL)
• Vitamins & trace elements: Add MVI-Pediatric and trace element solution

Enteral Nutrition

• Trophic feeds: 10–20 mL/kg/day of breast milk starting DOL 1–2 (primes the gut, promotes motility, does not increase NEC risk)
• Advancement: Increase by 20–30 mL/kg/day in stable preterm infants using standardized feeding protocols
• Full feeds: 140–160 mL/kg/day; target caloric intake 110–130 kcal/kg/day
• Human milk fortification: Add HMF (human milk fortifier) once feeds reach 80–100 mL/kg/day to provide additional protein (to 3.5–4 g/kg/day), calcium, phosphorus, and calories for preterm infants
• Growth target: 15–20 g/kg/day (approximates intrauterine growth rate)

17 Neonatal Hematology

Anemia of Prematurity

Anemia of prematurity (AOP) is a normocytic, normochromic anemia that develops in preterm infants over the first weeks of life, caused by low erythropoietin (EPO) production, shortened RBC lifespan (40–60 days), rapid body growth, and iatrogenic blood loss from laboratory draws. It is the most common anemia in preterm infants.

Transfuse with pRBC 10–20 mL/kg over 3–4 hours; use CMV-negative, irradiated, leukoreduced units. EPO (erythropoietin) with iron supplementation can reduce transfusion needs in stable preterm infants, but routine use remains controversial; iron supplementation (2–4 mg/kg/day) is universally recommended for preterm infants once on full enteral feeds.

Polycythemia

Defined as venous hematocrit >65%. Causes: delayed cord clamping, twin-to-twin transfusion, IDM, SGA, maternal-fetal transfusion, chromosomal abnormalities. Most are asymptomatic; symptomatic infants (lethargy, poor feeding, hypoglycemia, respiratory distress, cyanosis, seizures) may require partial exchange transfusion with normal saline to reduce Hct to ~55%. Asymptomatic polycythemia is managed with hydration and monitoring.

Neonatal Thrombocytopenia

Neonatal alloimmune thrombocytopenia (NAIT) is the platelet equivalent of hemolytic disease of the newborn. Maternal antibodies (most commonly anti-HPA-1a) cross the placenta and destroy fetal platelets. Unlike Rh disease, NAIT can occur in the first pregnancy. Treatment: transfusion with HPA-1a-negative platelets (or washed maternal platelets); IVIG; monitor for intracranial hemorrhage.

Hemolytic Disease of the Newborn

18 Congenital Heart Disease

Congenital heart disease (CHD) affects approximately 8–10 per 1,000 live births and is the leading cause of death from congenital anomalies. Classification into cyanotic vs. acyanotic lesions guides the initial clinical approach.

Cyanotic CHD — The 5 T’s

Acyanotic CHD

Hyperoxia Test

Used to differentiate cyanotic CHD from pulmonary disease: administer 100% FiO₂ for 10 minutes. In pulmonary disease, PaO₂ typically rises to >150 mmHg. In cyanotic CHD with fixed right-to-left shunt, PaO₂ remains <100 mmHg (often <70 mmHg) and SpO₂ does not significantly improve. This test is not definitive and echocardiography is required for diagnosis.

Prostaglandin E₁ (PGE₁) for Ductal-Dependent Lesions

Any neonate with suspected ductal-dependent CHD should receive PGE₁ to maintain ductal patency:

• Dose: 0.05–0.1 mcg/kg/min IV continuous infusion; may reduce to 0.01–0.025 mcg/kg/min once ductus is open
• Side effects: Apnea (10–12% — have intubation equipment ready), hypotension, fever, flushing, diarrhea
• Ductal-dependent for pulmonary blood flow: Pulmonary atresia, critical PS, tricuspid atresia, severe TOF
• Ductal-dependent for systemic blood flow: Critical coarctation, interrupted aortic arch, hypoplastic left heart syndrome
• Ductal-dependent for mixing: TGA

Critical CHD Screening

Pulse oximetry screening is performed on all newborns after 24 hours of life (or before discharge if earlier). Measure SpO₂ on the right hand (preductal) and either foot (postductal). A positive screen requires echocardiography: SpO₂ <90% in any extremity (immediate fail), SpO₂ 90–94% in both extremities or >3% difference between right hand and foot on 3 measures separated by 1 hour.

19 Patent Ductus Arteriosus

The patent ductus arteriosus (PDA) occurs in up to 70% of infants born <28 weeks gestation and is a major contributor to morbidity in preterm infants. As PVR falls postnatally, the shunt direction becomes left-to-right, causing pulmonary overcirculation and systemic hypoperfusion.

Clinical Signs of Hemodynamic Significance

• Continuous “machinery” murmur best heard at left upper sternal border (may be only systolic in preterm infants)
• Bounding peripheral pulses and wide pulse pressure (low diastolic BP)
• Hyperdynamic precordium
• Worsening respiratory status (increased ventilator requirements, inability to wean)
• Hepatomegaly, feeding intolerance
• Diastolic flow reversal in descending aorta on echo (sign of steal)

Echocardiographic Criteria

Hemodynamically significant PDA (hsPDA): duct diameter >1.5 mm (or >1.5 mm/kg), LA:Ao ratio >1.5, left ventricular dilation, diastolic flow reversal in the descending aorta, absent or reversed diastolic flow in the anterior cerebral or renal arteries.

Management

20 Neonatal Neurology

Intraventricular Hemorrhage (IVH)

IVH occurs in ~25–30% of VLBW infants, originating from the fragile germinal matrix vasculature. The germinal matrix is a highly vascularized region in the subependymal zone that involutes by 34–36 weeks; its vessels lack smooth muscle support and are vulnerable to fluctuations in cerebral blood flow.

Papile Grading System

Screening Protocol

Cranial ultrasound screening for all infants <32 weeks: DOL 3–7 (detect early IVH), DOL 10–14 (detect late IVH and early PVL), 36 weeks PMA or near discharge (detect PVL, post-hemorrhagic ventricular dilation). Repeat sooner if clinical deterioration (unexplained drop in Hct, bulging fontanelle, apnea/bradycardia).

Periventricular Leukomalacia (PVL)

PVL is ischemic injury to periventricular white matter, the most common brain injury associated with cerebral palsy in preterm infants. Cystic PVL (visible cysts on ultrasound) carries the worst prognosis but has decreased in incidence; non-cystic (diffuse) PVL is more common and may be detected only on MRI. Risk factors: chorioamnionitis, postnatal sepsis, hypotension, hypocapnia.

Neonatal Seizures

Treatment: Correct underlying cause (hypoglycemia, hypocalcemia, meningitis). Phenobarbital is first-line: loading dose 20 mg/kg IV (may give additional 10 mg/kg boluses × 2 if seizures persist, up to 40 mg/kg total). Second-line: levetiracetam (40–60 mg/kg IV), fosphenytoin (20 mg/kg PE IV), or midazolam infusion. Monitor with aEEG or continuous EEG — >50% of neonatal seizures are electrographic only (no clinical correlate).

Retinopathy of Prematurity (ROP)

ROP is a vasoproliferative disorder of the immature retina. The retina is vascularized centrifugally from the optic disc, completing nasally by ~36 weeks and temporally by ~40 weeks. Premature birth interrupts vascularization; subsequent hyperoxia suppresses VEGF → vascular growth arrest → then, as retinal metabolic demand increases, relative hypoxia triggers VEGF upregulation → abnormal neovascularization.

Plus disease: Dilated, tortuous posterior pole vessels; indicates active, aggressive disease and lowers the threshold for treatment. Aggressive posterior ROP (AP-ROP): Rapidly progressive disease in zone I or posterior zone II with prominent plus disease; requires urgent treatment.

Screening Criteria

Screen all infants <30 weeks GA or <1,500 g (and selected infants 30–36 weeks with unstable course). Initial exam at 31 weeks PMA or 4 weeks postnatal age, whichever is later. Follow-up per AAP/AAO guidelines based on zone and stage.

Treatment

• Laser photocoagulation: Ablates avascular retina to reduce VEGF drive; standard of care for type 1 ROP (zone I any stage with plus, zone I stage 3, zone II stage 2 or 3 with plus)
• Anti-VEGF therapy (bevacizumab/ranibizumab): Intravitreal injection; increasingly used for zone I disease and AP-ROP; allows continued peripheral vascularization (advantage over laser); requires long-term follow-up (late recurrence possible)

21 Prematurity & NICU Organization

Classification of Preterm Birth

Periviability & Limits of Viability

The “gray zone” of viability is generally 22 0/7 to 25 6/7 weeks. Management should be guided by individualized assessment (GA, estimated fetal weight, sex, singleton/multiple, antenatal steroids exposure) and family counseling using tools such as the NICHD Neonatal Research Network’s Extremely Preterm Birth Outcome Data tool. At 22 weeks, active resuscitation is offered based on institutional guidelines and family preferences; at 25 weeks, active resuscitation is standard of care at most centers.

Antenatal Interventions

• Antenatal corticosteroids: Betamethasone 12 mg IM × 2 doses 24 hours apart (or dexamethasone 6 mg IM × 4 doses 12 hours apart); for threatened preterm delivery at 24 0/7 to 33 6/7 weeks (may consider at 23 weeks); reduces RDS, IVH, NEC, and mortality; optimal benefit 48 hours to 7 days after administration; a single “rescue” course may be given if ≥14 days since prior course and delivery remains imminent
• Magnesium sulfate for neuroprotection: 4–6 g IV loading over 20–30 min, then 1–2 g/hr until delivery or for 24 hours; for impending delivery at <32 weeks; reduces risk of cerebral palsy by ~30–40% (NNT ~63)
• GBS prophylaxis: As detailed in section 11
• Tocolysis: Short-term to allow steroid administration; agents include nifedipine, indomethacin (<32 weeks), atosiban (outside US)

NICU Levels of Care

22 Congenital Anomalies

Tracheoesophageal Fistula / Esophageal Atresia

Incidence ~1:3,500. The most common type (85%, Type C) is esophageal atresia with a distal tracheoesophageal fistula (TEF). Presents with drooling, choking, cyanosis with first feed, inability to pass an orogastric tube (coils in proximal esophageal pouch on CXR). Gas in the stomach confirms a distal fistula; gasless abdomen suggests pure atresia (Type A).

Associated anomalies: VACTERL association (Vertebral, Anorectal, Cardiac, TE fistula, Renal, Limb). Management: suctioning of proximal pouch, upright positioning, IV fluids, antibiotics if pneumonia, surgical repair (primary anastomosis when possible).

Congenital Diaphragmatic Hernia (CDH)

Incidence ~1:2,500. Left-sided in 85% (Bochdalek hernia through the posterolateral defect). Abdominal viscera herniate into the thorax → pulmonary hypoplasia + pulmonary hypertension. Presents with scaphoid abdomen, absent breath sounds on affected side, mediastinal shift to contralateral side, respiratory distress at birth.

• Stabilization: Immediate intubation (avoid bag-mask — gastric distension worsens lung compression), OG tube to continuous suction, gentle ventilation with permissive hypercapnia, target preductal SpO₂ >85%
• PPHN management: iNO, sildenafil, milrinone as needed
• ECMO criteria: OI >40 or failure to maintain preductal SpO₂ >85% despite maximal therapy; typically VA ECMO
• Surgical repair: After hemodynamic stabilization (typically 24–72 hours); primary closure or patch repair

Gastroschisis vs. Omphalocele

Neural Tube Defects

Myelomeningocele (spina bifida cystica): Failure of neural tube closure exposing spinal cord and meninges; most common at lumbosacral level. Motor/sensory deficits below the level of the lesion, neurogenic bladder/bowel, Chiari II malformation (hindbrain herniation → hydrocephalus in 80–90%). Management: Moist sterile dressing over defect, prone positioning, early surgical closure (within 24–48 hours), VP shunt for hydrocephalus, ongoing multidisciplinary follow-up. Prevention: folic acid 400 mcg/day before conception (4 mg/day if prior affected pregnancy).

Chromosomal Anomalies

23 Neonatal Abstinence Syndrome

Neonatal abstinence syndrome (NAS), increasingly termed neonatal opioid withdrawal syndrome (NOWS), occurs in 55–94% of neonates exposed to opioids in utero. Incidence has risen dramatically with the opioid epidemic, from ~1.5 per 1,000 hospital births in 2004 to ~7 per 1,000 in 2014.

Clinical Features

Onset is typically 24–72 hours after birth for short-acting opioids (heroin) and 48–96 hours for long-acting opioids (methadone, buprenorphine). Symptoms span multiple systems:

• CNS: High-pitched cry, tremors (disturbed and undisturbed), irritability, seizures (rare), hypertonicity, poor sleep
• GI: Poor feeding, uncoordinated suck, vomiting, diarrhea, excessive weight loss
• Autonomic: Sneezing, yawning, nasal stuffiness, sweating, fever, mottling, tachypnea

Finnegan Neonatal Abstinence Scoring System

The modified Finnegan scoring tool assesses 21 items across CNS, metabolic, respiratory, and GI domains. Scored every 3–4 hours. Scores ≥8 on three consecutive assessments, or a single score ≥12, traditionally prompted pharmacologic treatment.

Eat-Sleep-Console (ESC) Approach

An increasingly adopted, function-based assessment that replaces the Finnegan score with three simple questions:

• Can the infant eat ≥1 oz per feed (or breastfeed well)?
• Can the infant sleep undisturbed for ≥1 hour?
• Can the infant be consoled within 10 minutes?

If yes to all three, no pharmacologic treatment is needed regardless of Finnegan score. ESC emphasizes non-pharmacologic care first and has reduced pharmacologic treatment rates by 50%, shortened hospital stays by 50%, and decreased NICU admissions.

Non-Pharmacologic Management (First-Line)

• Rooming-in with mother (reduces NAS severity and LOS)
• Swaddling, skin-to-skin contact, low-stimulation environment (dim lights, reduced noise)
• Frequent small feedings on demand
• Breastfeeding encouraged if mother is in stable medication-assisted treatment (MAT) program, HIV-negative, and not using illicit substances

Pharmacologic Treatment (When Non-Pharmacologic Fails)

24 Discharge Planning

Discharge from the NICU represents a critical transition. The preterm infant must meet several physiologic milestones and the family must be prepared for home care, follow-up, and monitoring.

Physiologic Criteria for Discharge

• Thermal stability: Maintain normal temperature in an open crib for ≥24–48 hours
• Feeding competence: Adequate oral feeding to sustain growth (breast or bottle); coordinated suck-swallow-breathe; consistent weight gain (20–30 g/day)
• Cardiorespiratory stability: No significant apnea, bradycardia, or desaturation events for 5–8 days (event-free period varies by institution); off supplemental O₂ or stable on home O₂

Car Seat Challenge

Recommended for all infants born <37 weeks before discharge. The infant is placed in their own car seat and monitored for 90–120 minutes (or the duration of the planned car ride home, whichever is longer). A fail is defined as: sustained desaturation <90%, bradycardia <80 bpm, or apnea >20 seconds. Options for failure include a car bed or repeat testing after clinical improvement.

Immunizations

• Hepatitis B vaccine: First dose within 24 hours of birth for all medically stable infants ≥2 kg; for infants <2 kg born to HBsAg-negative mothers, delay until 1 month of age or hospital discharge
• All routine childhood immunizations given at chronologic age (not corrected age), using standard doses regardless of weight at time of vaccination
• Palivizumab (Synagis): RSV monoclonal antibody; recommended for infants <29 weeks GA during first RSV season, infants with CLD or hemodynamically significant CHD; 15 mg/kg IM monthly during RSV season (October–March)

Screening Before Discharge

Follow-Up

• Pediatrician: Within 48–72 hours of discharge; weight check, feeding assessment, bilirubin if needed
• Developmental follow-up: High-risk infant follow-up clinic at 4, 8, 12, 18, 24 months corrected age; Bayley Scales of Infant Development at 18–24 months; early intervention referral as needed
• Ophthalmology: Continued ROP screening until retinal vascularization is complete
• Audiology: Repeat hearing assessment if risk factors (aminoglycosides, hyperbilirubinemia, congenital CMV)
• Home monitoring: Apnea monitors for selected infants (severe BRUE, siblings of SIDS, home O₂); pulse oximetry for infants on supplemental O₂

25 Scoring Systems

APGAR Score

New Ballard Score

Total score range: −10 to 50. Score mapped to gestational age: −10 = 20 weeks, 0 = 26 weeks, 10 = 30 weeks, 20 = 34 weeks, 30 = 38 weeks, 40 = 42 weeks, 50 = 44 weeks.

Sarnat Staging (HIE)

Modified Bell Staging (NEC)

Papile IVH Grading

Finnegan Neonatal Abstinence Scoring (Abbreviated)

Score ≥8 on 3 consecutive assessments or single score ≥12 traditionally indicates need for pharmacologic treatment. Total possible score ~45.

ROP Staging

26 Medications Master Table

27 Normal Neonatal Values

Vital Signs by Gestational Age

Rule of thumb: mean BP (mmHg) should approximate gestational age in weeks during the first days of life (e.g., 28 weeks GA → target MAP ~28 mmHg).

Laboratory Reference Ranges

CSF Values

Blood Gas Values

28 Abbreviations Master List