Neonatal Jaundice: MCCQE1 Preparation Guide

Introduction

Neonatal jaundice (hyperbilirubinemia) is one of the most common clinical conditions encountered in newborns. For Canadian medical students and international medical graduates preparing for the MCCQE1, understanding the nuances of screening, diagnosis, and management according to Canadian Paediatric Society (CPS) guidelines is essential.

Approximately 60% of term and 80% of preterm newborns develop clinical jaundice. While most cases are benign, failure to identify and treat severe hyperbilirubinemia can lead to kernicterus (chronic bilirubin encephalopathy), a devastating and preventable condition.

Pathophysiology of Bilirubin

Understanding the metabolism of bilirubin is crucial for distinguishing between unconjugated and conjugated hyperbilirubinemia.

Classification of Jaundice

For MCCQE1, you must quickly categorize jaundice based on timing and type (Conjugated vs. Unconjugated).

1. Physiologic vs. Pathologic Jaundice

2. Breastfeeding vs. Breast Milk Jaundice

This is a classic high-yield topic for the MCCQE1.

Clinical Assessment

History

• Family History: Anemia, splenectomy, jaundice in siblings (suggests hemolysis).
• Maternal History: Blood type (O+ mothers), Rh status, antibodies.
• Pregnancy/Delivery: TORCH infections, traumatic delivery (cephalohematoma $\to$ RBC breakdown).
• Feeding: Breast vs. bottle, frequency, voids, stools.

Physical Examination

• Visual Inspection: Jaundice progresses cephalocaudally (Head $\to$ Trunk $\to$ Extremities). Note: Visual estimation is inaccurate and TcB/TSB is required.
• Hydration Status: Fontanelles, mucous membranes, skin turgor.
• Signs of Hemolysis: Pallor, hepatosplenomegaly.
• Extravascular Blood: Cephalohematoma or bruising.
• Stool Color: Pale or acholic stools are a “Red Flag” for Biliary Atresia.

Canadian Guidelines for Screening and Management

The Canadian Paediatric Society (CPS) guidelines are the gold standard for your MCCQE1 preparation.

Screening

1. Universal Screening: All newborns should be screened for bilirubin (Total Serum Bilirubin [TSB] or Transcutaneous Bilirubin [TcB]) between 24 and 72 hours of life.
2. Timing: Usually performed at the time of the metabolic screening test.
3. Visual Assessment: Not sufficient for ruling out significant hyperbilirubinemia.

Risk Stratification

Use the Bhutani Nomogram (or Canadian adaptations) to plot TSB levels against age in hours. This determines the risk of developing severe hyperbilirubinemia.

Major Risk Factors (CPS):

• Jaundice in first 24 hours.
• ABO/Rh incompatibility with positive Direct Antiglobulin Test (DAT/Coombs).
• Gestational age < 37 weeks.
• Previous sibling received phototherapy.
• Cephalohematoma or significant bruising.
• Exclusive breastfeeding with suboptimal intake.
• East Asian race.

Investigations Checklist

Use this task list to guide your workup for a jaundiced neonate on the MCCQE1:

• Total and Direct Bilirubin: To differentiate conjugated vs. unconjugated.
• Blood Group and Coombs (DAT): Mother and Baby.
• CBC and Smear: Check for hemoglobin (anemia), reticulocytes (hemolysis), and RBC morphology (spherocytes).
• G6PD Screen: If high risk ethnicity (Mediterranean, Middle Eastern, African, Southeast Asian).
• Albumin: Bilirubin binds to albumin; low albumin increases risk of free bilirubin toxicity.
• Septic Workup: If clinical signs of sepsis are present.
• Thyroid/Metabolic Screen: For prolonged jaundice.

Management Strategies

1. Phototherapy

• Mechanism: Photoisomerization converts toxic unconjugated bilirubin into a water-soluble isomer (lumirubin) that can be excreted without conjugation.
• Indication: Based on treatment graphs (TSB vs. Age in hours) stratified by risk (Low, Medium, High).
• Light Specs: Blue-green spectrum (wavelength ~460 nm).
• Nursing Care: Protect eyes, maximize skin exposure, ensure hydration.

2. Exchange Transfusion

• Indications:
  • Acute bilirubin encephalopathy.
  • TSB continues to rise despite intensive phototherapy.
  • TSB levels exceed the exchange transfusion threshold on the nomogram.
• Mechanism: Removes bilirubin and antibodies; corrects anemia.

3. Intravenous Immunoglobulin (IVIG)

• Indication: Isoimmune hemolytic disease (Rh or ABO incompatibility) with rising TSB despite phototherapy.
• Effect: Reduces the need for exchange transfusion.

4. Management of Conjugated Hyperbilirubinemia

Complications: Kernicterus

Kernicterus is the chronic, permanent sequelae of bilirubin toxicity. It affects the basal ganglia and brainstem nuclei.

Clinical Features of Acute Bilirubin Encephalopathy (ABE):

1. Early: Lethargy, hypotonia, poor suck.
2. Intermediate: Hypertonia (retrocollis, opisthotonos), fever, high-pitched cry.
3. Advanced: Seizures, coma, death.

Chronic Kernicterus Tetrad:

1. Choreoathetoid cerebral palsy.
2. Sensorineural hearing loss.
3. Gaze abnormality (upward gaze palsy).
4. Dental enamel dysplasia.

Key Points to Remember for MCCQE1

• Jaundice < 24 hours is a medical emergency requiring immediate workup.
• Conjugated hyperbilirubinemia is never physiologic. Think Biliary Atresia or Neonatal Hepatitis.
• Breastfeeding Jaundice = “Starvation” jaundice (early). Breast Milk Jaundice = Factor in milk (late).
• ABO Incompatibility: Most common cause of hemolytic disease in newborns. Occurs with Group O mothers and Group A or B infants. Can occur in the first pregnancy (unlike Rh).
• Prolonged Jaundice (> 2 weeks in term): Must fractionate bilirubin. If conjugated is normal, check thyroid (hypothyroidism) and urine (UTI).

Sample Question

Scenario

A 36-hour-old female infant born at 39 weeks gestation is noted to be jaundiced. The pregnancy was uncomplicated. The mother’s blood group is O positive. The infant is exclusively breastfed and has voided twice with one meconium stool. On examination, the infant is alert but appears jaundiced to the lower abdomen. There is no cephalohematoma. Vital signs are stable.

Laboratory results:

• Infant Blood Group: A positive
• Direct Antiglobulin Test (DAT): Positive
• Total Serum Bilirubin (TSB): 280 µmol/L
• Direct Bilirubin: 4 µmol/L

According to the Canadian Paediatric Society guidelines, which of the following is the most appropriate next step in management?

Options

• A. Discontinue breastfeeding and start formula for 48 hours
• B. Initiate intensive phototherapy
• C. Perform an exchange transfusion immediately
• D. Reassure the parents and repeat TSB in 24 hours
• E. Administer intravenous immunoglobulin (IVIG)

Explanation

The correct answer is:

• B. Initiate intensive phototherapy

Detailed Explanation: This clinical scenario describes a newborn with ABO incompatibility (Mother O, Baby A, DAT positive). This places the infant in a higher risk category for severe hyperbilirubinemia due to hemolysis.

• Analysis: At 36 hours of life, a TSB of 280 µmol/L in an infant with risk factors (hemolysis) typically falls above the treatment threshold for phototherapy on standard Canadian nomograms. Immediate initiation of phototherapy is required to prevent further rise and potential neurotoxicity.
• Why A is incorrect: Interruption of breastfeeding is generally not recommended as a first-line treatment. The focus should be on treating the jaundice while supporting breastfeeding (or supplementing if dehydration is severe, which is not indicated here).
• Why C is incorrect: Exchange transfusion is reserved for infants with signs of acute bilirubin encephalopathy or TSB levels significantly higher than the phototherapy threshold (often > 375-400 µmol/L at this age depending on risk) or failure of phototherapy.
• Why D is incorrect: Waiting 24 hours is dangerous. This is hemolytic jaundice, and levels can rise rapidly.
• Why E is incorrect: IVIG is indicated if the TSB is rising despite intensive phototherapy or if the TSB is within 30-50 µmol/L of the exchange transfusion threshold. It is not the initial step before starting phototherapy.

References

1. Canadian Paediatric Society (CPS). Guidelines for detection, management and prevention of hyperbilirubinemia in term and late preterm newborn infants. Paediatrics & Child Health, 2007 (Reaffirmed 2018). Available at: https://cps.ca/en/documents/position/hyperbilirubinemia-newborn 
2. Medical Council of Canada. MCCQE Part I Objectives: Neonatal Jaundice.
3. Bhutani VK, et al. Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns. Pediatrics. 1999.
4. Toronto Notes 2024. Pediatrics Chapter: Neonatology.