The Preterm Newborn

1. Define preterm labor and classify immaturity and birth weight

Preterm Birth: Delivery before the completion of the 37th week of gestation ($< 37+0$ weeks).
Newborn: An infant in the first 28 days of life.
Prematurity: The leading cause of neonatal morbidity and mortality; risk decreases as gestational age increases.

Classification by Gestational Age:

Classification by Birth Weight (BW):

Low Birth Weight (LBW): < 2500 g
Very Low Birth Weight (VLBW): 1000–1499 g
Extremely Low Birth Weight (ELBW): < 1000 g
Note: Low weight can result from prematurity, Intrauterine Growth Restriction (IUGR/SGA), or both.

Respiratory Immaturity: Structural and functional immaturity, surfactant deficiency, decreased lung compliance, and alveolar collapse. High risk for Respiratory Distress Syndrome (RDS) and apnea of prematurity.
Thermoregulation Immaturity: High surface area-to-weight ratio, minimal subcutaneous fat, and reduced heat production. Highly susceptible to hypothermia, which worsens metabolic stability.
CNS Immaturity: Poorly coordinated suck-swallow-breathe reflex; highly vulnerable germinal matrix leads to increased risk of Intraventricular Hemorrhage (IVH) and subsequent Periventricular Leukomalacia (PVL).
Gastrointestinal Immaturity: Limited motility and enzymatic activity. High risk of Necrotizing Enterocolitis (NEC) and intolerance to enteral feeding.
Metabolic/Homeostatic Immaturity: Limited glycogen reserves (hypoglycemia) and immature liver conjugation (exaggerated hyperbilirubinemia/risk of kernicterus).
Immune Immaturity: Lower levels of maternal IgG (transferred in the 3rd trimester), thin skin barrier, and immature cellular immunity; high susceptibility to sepsis.
Vision/Long-term: Risk of Retinopathy of Prematurity (ROP) due to abnormal retinal vascularization.

Skin: Thin, deep red, shiny, translucent; visible veins; little to no vernix caseosa; abundant lanugo; minimal subcutaneous fat.
Head/Ears: Soft, unformed ear pinnae (lack of cartilage).
Extremities: Fingernails do not reach fingertips; minimal creasing on palms and soles; hypotonia (floppy posture).
Trunk: Relatively large abdomen; thick, gelatinous umbilical cord attached closer to the symphysis.
Breasts: Small/absent nipples; minimal or no areola.
Genitalia: Males: Undescended testes, smooth scrotum. Females: Labia majora do not cover the labia minora.
Behavior: Weak cry, lethargy, decreased spontaneous activity.

Mechanism: Surfactant deficiency.
Clinic: Tachypnea, grunting, nasal flaring, retractions, cyanosis.
Treatment: CPAP or mechanical ventilation, oxygen therapy, and exogenous surfactant administration.

Mechanism: Immaturity of the respiratory center in the brainstem.
Clinic: Respiratory pauses > 20 seconds, often with desaturation and bradycardia.
Treatment: Caffeine citrate, respiratory support (high-flow/CPAP).

Mechanism: Chronic lung injury from oxygen toxicity and barotrauma/volutrauma in immature lungs.
Diagnosis: Need for O2 or respiratory support at 36 weeks postmenstrual age.
Treatment: Gentle ventilation strategies, long-term home oxygen, diuretics.

Clinic: Systolic murmur, bounding pulses (wide pulse pressure), tachycardia.
Diagnosis: Echocardiography.
Treatment: Fluid restriction, Ibuprofen or Paracetamol; surgical ligation if medical therapy fails.

Mechanism: Fragile vessels in the germinal matrix rupture due to fluctuations in blood pressure.
Diagnosis: Cranial ultrasound.
Treatment: Supportive care, prevention of perfusion swings, monitoring for post-hemorrhagic hydrocephalus.

Clinic: Abdominal distension, vomiting (bilious), bloody stools, signs of sepsis.
Diagnosis: X-ray (Pneumatosis intestinalis), ultrasound.
Treatment: NPO (nothing by mouth), gastric decompression, broad-spectrum antibiotics, surgery if perforation occurs.

Mechanism: Frequent blood draws (iatrogenic), short RBC lifespan, and low erythropoietin.
Treatment: Iron supplementation, Erythropoietin, or RBC transfusion.

Mechanism: Inadequate calcium (Ca) and phosphorus (P) transfer (usually occurs in the 3rd trimester).
Clinic: Elevated ALP (Alkaline Phosphatase), fractures.
Prevention: Ca/P supplementation, Vitamin D, and breast milk fortification.