Model Answer
0 min readIntroduction
Physiological jaundice is a common condition observed in newborns, characterized by visible yellowing of the skin and sclera due to elevated levels of unconjugated bilirubin in the blood. This is a normal transitional phenomenon occurring in approximately 60-80% of term infants and a higher percentage in preterm infants. It arises from the immaturity of the newborn’s bilirubin metabolism system and the increased breakdown of fetal red blood cells. Understanding the underlying physiology, predisposing factors, and potential effects is crucial for appropriate neonatal care and prevention of complications.
Definition of Physiological Jaundice
Physiological jaundice is a transient increase in serum unconjugated bilirubin levels in the neonatal period, typically appearing on the 2nd or 3rd day of life and resolving within the first week. Bilirubin is a breakdown product of heme, released during the normal destruction of red blood cells. In newborns, several factors contribute to this transient hyperbilirubinemia, making it a physiological rather than pathological process within certain limits.
Underlying Physiology
The increased bilirubin levels in newborns are due to a combination of factors:
- Increased Bilirubin Production: Newborns have a higher red blood cell mass and a shorter red blood cell lifespan (approximately 80-90 days compared to 120 days in adults), leading to increased heme breakdown.
- Immature Uridine Diphosphate Glucuronosyltransferase (UDPGT): The liver enzyme UDPGT is responsible for conjugating unconjugated bilirubin, making it water-soluble for excretion. This enzyme is relatively inactive at birth and takes several days to reach adult levels.
- Increased Enterohepatic Circulation: Newborns have increased reabsorption of bilirubin from the intestines back into the circulation due to a lack of intestinal flora and increased permeability.
- Decreased Excretion: Newborns have limited ability to excrete bilirubin in bile.
Predisposing Causes
While physiological jaundice is common, certain factors can increase the risk or severity:
Maternal Factors
- Blood Group Incompatibility (Rh or ABO): Maternal antibodies against fetal red blood cell antigens can cause hemolysis.
- Gestational Diabetes: Associated with increased bilirubin production.
- Maternal Infections: Can affect fetal red blood cell lifespan.
Infant Factors
- Preterm Birth: Immature liver function and increased red blood cell fragility.
- Cephalohematoma or Bruising: Increased bilirubin production from breakdown of blood in these areas.
- Polycythemia: Increased red blood cell mass.
- Genetic Predisposition: Variations in the UDPGT gene (e.g., Gilbert’s syndrome) can affect bilirubin metabolism.
- Breastfeeding: Two types – Breastfeeding Jaundice (inadequate intake leading to dehydration and increased enterohepatic circulation) and Breast Milk Jaundice (substances in breast milk inhibiting UDPGT).
Environmental Factors
- Exposure to Oxidative Stress: Can increase red blood cell breakdown.
Effects of Physiological Jaundice
The effects of physiological jaundice depend on the bilirubin level and the infant’s overall health.
Benign Effects
- Visible Jaundice: The primary and most noticeable effect.
- Lethargy: Mild drowsiness may be observed.
Potentially Harmful Effects
If bilirubin levels become excessively high, it can lead to:
- Kernicterus: Bilirubin-induced neurological dysfunction, resulting in irreversible brain damage. This occurs when unconjugated bilirubin crosses the blood-brain barrier and deposits in the basal ganglia.
- Acute Bilirubin Encephalopathy: An acute manifestation of bilirubin toxicity, characterized by hypertonia, arching of the back, high-pitched cry, and feeding difficulties.
- Long-Term Neurological Sequelae: Cerebral palsy, hearing loss, and cognitive impairment can result from kernicterus.
| Bilirubin Level (mg/dL) | Risk Level | Intervention |
|---|---|---|
| < 8 | Low | Observation |
| 8-12 | Moderate | Increased feeding, phototherapy consideration |
| >12 | High | Intensive phototherapy, exchange transfusion consideration |
Conclusion
Physiological jaundice is a common and usually benign condition in newborns, stemming from the immature bilirubin metabolism system. However, recognizing predisposing factors and monitoring bilirubin levels are crucial to prevent potentially devastating neurological complications like kernicterus. Effective management involves adequate hydration, appropriate feeding practices, and timely intervention with phototherapy or exchange transfusion when indicated. Ongoing research focuses on optimizing bilirubin monitoring and developing strategies to minimize the risk of severe hyperbilirubinemia.
Answer Length
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