🔑 Key Learning

  • The abnormal fluid accumulation in two or more foetal compartments, including ascites, pleural effusion, pericardial effusion, and subcutaneous edema. It is an end-stage manifestation of various underlying conditions, leading to severe foetal anaemia, heart failure, and hypoxia.
  • Most cases are non-immune (>85%) – think thalassaemia, parvovirus B19, and cardiac causes first.
  • Look for clues: maternal infection, ethnicity, family history, previous foetal losses.

🧬 Pathophysiology

Hydrops fetalis is defined as abnormal accumulation of fluid in two or more foetal compartments, such as:

  • Ascites
  • Pleural effusion
  • Pericardial effusion
  • Skin oedema (>5 mm)

This leads to foetal heart failure, hypoxia, and ultimately, intrauterine death if untreated.

🧪 Classification

1. Immune Hydrops (Alloimmune Haemolysis)

  • Caused by Rh incompatibility (most commonly anti-D antibodies).
  • Clue: Rh-negative mother, second pregnancy, no anti-D prophylaxis.
  • Mechanism: Maternal anti-D antibodies cross placenta → haemolysis of Rh-positive foetal RBCs → severe anaemia → heart failure → hydrops.

2. Non-Immune Hydrops (NIHF)

Accounts for >85% of cases.

🩸 Haematologic Causes

  • Alpha thalassaemia major (Hb Barts)
    • Clue: Southeast Asian descent, early losses.
    • Mechanism: No alpha chains → ineffective Hb → hypoxia, anaemia.

❤️ Cardiac Causes

  • Structural congenital heart disease
  • Clue: Bradycardia/tachycardia or abnormal foetal echocardiogram.

🦠 Infectious Causes

  • Parvovirus B19
    • Clue: Recent contact with child with “slapped cheek” rash.
    • Mechanism: Aplastic anaemia due to red cell aplasia.
  • TORCH infections:
    • Toxoplasmosis, Other (syphilis), Rubella, CMV, Herpes
    • Clue: Flu-like illness, hepatosplenomegaly, intracranial calcifications.

🧬 Genetic/Chromosomal Causes

  • Turner Syndrome (45,X) and Noonan Syndrome
    • Mechanism: Lymphatic dysplasia → fluid accumulation.

👀 Clinical Features

  • Skin oedema (>5 mm)
  • Pleural effusion
  • Pericardial effusion
  • Ascites
  • Polyhydramnios
  • Placental thickening
  • Elevated MCA peak systolic velocity (MCA-PSV) → Suggestive of foetal anaemia
Newborn infant with Rhesus disease / severe hemolytic disease. Attribution: Benkerroum Zineb, Lachiri Boutaina, Lazrak Ikram, Moussaoui Rahali Driss, Dehayni Mohammed - https://panafrican-med-journal...

     

📝 Exam Clues & Clinchers

  • Rh-ve mother, second pregnancy, no anti-D → Think alloimmune haemolysis
  • Southeast Asian family history + recurrent early losses → Suspect alpha-thalassaemia
  • MCA Doppler raised → Suggests foetal anaemia
  • Contact with slapped-cheek rash child → Think Parvovirus B19