Hydrops fetalis

Hydrops fetalis is a situation where there is an accumulation of fluid + / - oedema involving at least two fetal components. This may manifest as a

• fetal pleural effusion
• fetal pericardial effusion
• generalised body oedema - fetal anasarca / nuchal oedema / cystic hygroma
• fetal ascites

Epidemiology

The estimated incidence is at ~ 1 in 2000 births although this can signifcantly vary according to different regions.

Pathology

It is considered a prenatal form of cardiac failure. It was traditionally divided into two broad groups

• immune hydrops fetalis (IHF)
• non immune hydrops fetalis (NIHF)

Causes include

Immune hydrops

Accounts for the minority (~ 10%) of cases in present day pregnancies ⁸ : although historically accounted for large proportion of cases in the early to mid 20^th century

• feto maternal blood group incompatibility (including rhesus incompatibility) : erythroblastosis fetalis

Non immune hydrops

Accounts for the majority of cases and can arise from protean causes which include

• chromosomal anomalies
  • Turner syndrome
  • trisomies 
    • trisomy 13
    • trisomy 18
    • trisomy 21
• cardiac causes
  • abnormalities in fetal heart rate :  e.g. fetal tachyarrhythmias
  • congenital cardiac anomalies
  • fetal cardiac tumours : cardiac rhabdomyoma
• twin pregnancy related complications
  • twin to twin transfusion syndrome : in recipient twin
  • twin reversed arterial perfusion sequence : in pump twin
• in utero infection(s)
  • congenital viral infection(s)
    • TORCH group
    • fetal parvovirus B19 infection : considered the most common infectious cause of hydrops
    • coxsackie viral infection
• fetal tumours capable of producing significant AV shunts ³
  • sacrococcygeal teratoma
• inborn errors of metabolism
  • Gaucher disease
  • Niemann-Pick disease
• fetal hypoproteinaemic states
  • congenital nephrotic syndrome
• congenital / fetal anaemia(s)
  • alpha thalassaemia ⁸ : can be relatively common cause in south east asia
• fetal skeletal dysplasia(s) ¹⁰
• fetal lymphovascular anomalies
  • cystic hygroma ⁸
• high output flow states
  • vein of Galen aneurysmal malformation
  • umbilical vein thrombosis in cases of umbilical vein varix.
• thoracic / pulmonary abnormalities : thought to be from fetal venous obstruction
  • primary fetal hydrothorax
  • congenital pulmonary airways malformation ¹¹
  • congenital diaphragmatic herniation ¹¹

Radiographic features

Antenatal ultrasound

Sonographic features can be similar for both immune and non - immune hydrops and include

• increased amniotic fluid volumes
• increased nuchal translucency (especially 1^st trimester ⁵)
• larger placental size (placentomegaly) / increased placental thickness (placental oedema)
• presence of a fetal pleural or pericardial effusion
• generalised fetal body swelling - fetal anasarca
• umbilical venous dilatation

Prognosis

The overall prognosis can be variable, dependant on the underlying cause.

Etymology

The term hydrops fetalis comes from the Latin meaning oedema of the fetus ⁶