Study sheet: Physiological Neonatal Jaundice

📋 Course Outline

1. Jaundice Definitions and Frequency
2. Bilirubin Production and Metabolism
3. Why Newborns Develop Jaundice
4. Typical Physiological Jaundice
5. Recognising Jaundice and Risk
6. Bilirubin Assessment and Measurement
7. Complications and Treatment
8. Prolonged Jaundice and Breastfeeding

📖 1. Jaundice Definitions and Frequency

🔑 Key Concepts & Definitions

• Jaundice : a yellow colouration of the skin and sclerae caused by the accumulation of bilirubin after red blood cell breakdown.
• Kernicterus : the clinical features of acute or chronic bilirubin encephalopathy, including cerebral palsy, hearing loss and visual problems.
• Term baby : born at 37 weeks or more of gestational age.

📝 Essential Points

• Approximately 60% of term babies and 80% of preterm babies develop jaundice during the first week of life, and it is harmless in most babies. — NICE, 2010

💡 Memory Hook

Physiological jaundice is usually transient and harmless, whereas pathological jaundice may signal serious disease.

📖 2. Bilirubin Production and Metabolism

★ Must-know

• Ageing, immature or malformed red blood cells are removed by phagocytosis in the reticuloendothelial system, including the liver, spleen and macrophages.

• Haemoglobin is separated into:

  • haem
  • globin
  • iron

• In the liver, unconjugated bilirubin is conjugated using oxygen, glucose and enzymes, producing water-soluble conjugated bilirubin that can be excreted into bile and the gut.

• In the gut, bacteria convert conjugated bilirubin to urobilin, which is excreted in faeces, while some bilirubin is reabsorbed through enterohepatic circulation and some is excreted in urine.

Further detail

• Unconjugated bilirubin combines with albumin and is transported in the bloodstream to the liver, where carrier proteins Y and Z facilitate hepatic uptake.

💡 Memory Hook

Red cell breakdown → albumin transport → liver conjugation → gut excretion.

📖 3. Why Newborns Develop Jaundice

★ Must-know

• Fetal haemoglobin contains a pair of gamma-globin molecules instead of the beta-globins typical of adult haemoglobin and binds oxygen with greater affinity.

• Fetal red blood cells have a life span of 70–80 days at term and are removed after birth as fetal haemoglobin is replaced by adult haemoglobin.

• The main contributing factors are:

  • short-lived red blood cells
  • limited albumin binding
  • a sterile gut
  • poor peristalsis
  • an immature liver

Further detail

• The fetus compensates for the placenta's relatively poor oxygenation by producing approximately 7 million red blood cells per mm3.

💡 Memory Hook

Short-lived fetal red cells and immature hepatic and intestinal function → bilirubin accumulation.

📖 4. Typical Physiological Jaundice

★ Must-know

• Physiological jaundice usually begins around day 3, peaks around day 5 and lasts until approximately day 8.

📌 In typical physiological jaundice, bilirubin levels should not exceed approximately 200–215 μmol/l.

Further detail

• Physiological jaundice affects approximately 60% of term babies and 80% of preterm babies. — NICE, 2010

💡 Memory Hook

Day 3 onset → day 5 peak → approximately day 8 resolution.

📖 5. Recognising Jaundice and Risk

📝 Essential Points

• Clinical assessment includes:
  • yellow skin or sclerae
  • lethargy
  • poor feeding
  • pale stools
  • altered stool frequency
  • dark urine

📌 Jaundice appearing within the first 24 hours of life is pathological until proven otherwise and requires immediate referral to a paediatrician. — NICE, 2010

• Babies are more likely to develop significant hyperbilirubinaemia if they are under 38 weeks' gestation, have a sibling who required phototherapy, are intended to be exclusively breastfed or have visible jaundice in the first 24 hours. — NICE, 2010

📌 All babies should be examined for jaundice at every opportunity, especially during the first 72 hours, and babies with risk factors should receive an additional professional visual examination during the first 48 hours. — NICE, 2010

💡 Memory Hook

Jaundice in the first 24 hours requires urgent referral, whereas typical physiological jaundice appears around day 3 in a well baby.

📖 6. Bilirubin Assessment and Measurement

★ Must-know

• Jaundice generally progresses in a caudal direction from the head towards the feet, but visual inspection is a poor predictor of bilirubin severity.

📌 For babies aged over 24 hours with a gestational age of 35 weeks or more, use a transcutaneous bilirubinometer, confirm readings above 250 μmol/l with serum bilirubin, and use serum measurement at or above treatment thresholds. — NICE, 2016

📌 Serum bilirubin should be measured urgently within 6 hours in all babies over 24 hours old with suspected or obvious jaundice and used to determine management. — NICE, 2010

Further detail

📌 Visual inspection should be performed with the naked baby in bright, preferably natural light, examining the sclerae and gums and lightly pressing the skin to assess blanching. — NICE, 2016

💡 Memory Hook

Visual inspection detects jaundice but does not reliably measure its severity; bilirubin measurement is required.

📖 7. Complications and Treatment

🔑 Key Concepts & Definitions

• Bilirubin encephalopathy : neurological dysfunction caused by unconjugated bilirubin toxicity in the brain and spinal cord.

★ Must-know

• Kernicterus is most likely when serum bilirubin exceeds 350 μmol/l, and the risk is increased by prematurity and other risk factors.

• Risk criteria include serum bilirubin above 340 μmol/l in babies over 37 weeks' gestation and a rapidly rising bilirubin concentration of 8.5 μmol/l per hour. — NICE, 2010

📌 The stated threshold for exchange blood transfusion is 450 μmol/l.

Further detail

• Clinical features include:
  • a high-pitched cry
  • lethargy or unresponsiveness
  • hypertonia
  • rigidity and back arching
  • convulsions
  • athetosis
  • deafness
  • limited upward gaze
  • dental dysplasia
  • intellectual difficulties

💡 Memory Hook

Unconjugated bilirubin crosses the blood–brain barrier → bilirubin encephalopathy and kernicterus.

📖 8. Prolonged Jaundice and Breastfeeding

🔑 Key Concepts & Definitions

• Breastmilk jaundice : the normal and regularly occurring persistence of unconjugated hyperbilirubinaemia into the third and later weeks in an otherwise healthy breastfed newborn.

★ Must-know

• For jaundice lasting more than 14 days in babies born at 37 weeks or more, or more than 21 days in babies born before 37 weeks, assess stool and urine colour, measure conjugated bilirubin, perform blood and urine investigations, and confirm routine metabolic screening. — NICE, 2010

📌 Breastfeeding can usually continue during neonatal jaundice, and optimal breastfeeding that limits early weight loss and promotes early weight gain is associated with less breastfeeding jaundice.

Further detail

• Phototherapy converts bilirubin in the skin into isomers or oxidised bilirubin that can be excreted without conjugation, although most conversion is excreted slowly over 12–21 hours.

• Care during phototherapy must address:

  • eye protection
  • temperature regulation
  • nutrition and fluid management
  • increased bowel action and fluid loss
  • maternal bonding
  • reversible bronze pigmentation

💡 Memory Hook

Breastmilk jaundice can be a normal extension of unconjugated jaundice, whereas pale stools or dark urine suggest disease.

📊 Synthesis Tables

Jaundice Categories by Timing

Category	Timing	Significance
Physiological jaundice	Around day 3; peaks day 5; lasts approximately to day 8	Usually transient and harmless
Jaundice in the first 24 hours	Within the first day of life	Pathological until proven otherwise; urgent referral
Prolonged jaundice in term babies	More than 14 days	Requires investigation
Prolonged jaundice in preterm babies	More than 21 days	Requires investigation