What is the management plan for a fetus with an absent ductus venosus?

Management of Absent Ductus Venosus

When absent ductus venosus is diagnosed prenatally, immediate comprehensive evaluation for associated anomalies is essential, including detailed anatomic ultrasound, fetal echocardiography, and genetic testing with chromosomal microarray analysis, as this rare vascular anomaly carries a 24-33% risk of major malformations, chromosomal aberrations, and hydrops fetalis. 1, 2

Initial Diagnostic Workup

Detailed Anatomic Assessment

• Perform a comprehensive anatomic ultrasound (CPT 76811) to identify the specific pattern of abnormal venous circulation, as three main patterns exist with varying prognoses 1, 2:
  • Type 1 (46% of cases): Umbilical vein bypasses liver and connects directly to right atrium—carries the worst prognosis with highest risk of heart failure 1, 3
  • Type 2 (25% of cases): Umbilical vein bypasses liver and connects to inferior vena cava through iliac or renal veins 1, 2
  • Type 3 (21% of cases): Umbilical vein connects to portal circulation without ductus venosus formation 1

Fetal Echocardiography

• Obtain detailed fetal echocardiography to assess for cardiac anomalies and evaluate cardiovascular function, as absent ductus venosus is associated with high-cardiac output states and potential hemodynamic compromise 4
• Assess for cardiomegaly, valvular regurgitation, and signs of cardiac dysfunction, as unexplained cardiomegaly is a key finding 3
• Calculate cardiothoracic ratio (normal 0.25-0.35 using area) to quantify cardiac enlargement 4

Genetic Testing

• Offer chromosomal microarray analysis via amniocentesis, as chromosomal aberrations occur in 24% of cases, including Turner syndrome and Noonan syndrome 1, 2
• This recommendation aligns with SMFM guidelines for genetic testing when fetal malformations are present 4

Associated Anomalies Screening

• Systematically evaluate for commonly associated malformations including facial clefts, hemivertebrae, cardiac defects, genitourinary anomalies, and gastrointestinal anomalies 3
• Check for single umbilical artery, which should prompt detailed examination of umbilical and portal veins 3
• Assess for absence of portal vein, which occurs in 50% of cases examined postnatally 1

Serial Surveillance Protocol

Monitoring for Hydrops Development

• Implement intensive serial ultrasound surveillance every 1-2 weeks to monitor for hydrops fetalis, which develops in 33% of cases and indicates severe cardiovascular compromise 1, 5
• Hydrops can develop as early as the second trimester or as late as 36 weeks gestation 5
• Pay particular attention to hydrothorax, which can be extreme in affected fetuses 5

Cardiovascular Monitoring

• Perform serial fetal echocardiography to assess cardiac function and detect early signs of heart failure 4
• Monitor for ventricular wall shortening (normal >28% by M-mode), valvular regurgitation, and umbilical vein pulsations 4
• Heart failure appears particularly frequent when absent ductus venosus is associated with extrahepatic connections (Types 1 and 2) 1, 6

Doppler Assessment

• Serial Doppler evaluation is not routinely indicated unless fetal growth restriction develops, as ductus venosus abnormalities with normal umbilical artery Doppler suggest alternative pathophysiology related to vascular or genetic abnormalities rather than placental disease 4, 7

Delivery Planning

Timing Considerations

• For isolated absent ductus venosus without hydrops or other anomalies, delivery at term (37-39 weeks) is reasonable 6
• If hydrops develops, consider earlier delivery after administration of antenatal corticosteroids and consultation with neonatology 5
• Anticipate delivery if signs of in utero heart failure develop 2

Mode of Delivery

• Plan delivery at a tertiary care center with immediate access to neonatal intensive care and pediatric cardiology 3
• Mode of delivery should be determined based on standard obstetric indications and presence of hydrops 6

Neonatal Preparation

• Coordinate with neonatal team regarding potential need for immediate postnatal cardiovascular support, as mortality in isolated cases is approximately 20% 1
• Arrange postnatal imaging to confirm portal vein status, as absence occurs in 50% of affected infants 1

Prognostic Counseling

Risk Stratification

• Overall prognosis depends critically on three factors: pattern of venous circulation, presence of associated malformations, and chromosomal status 1, 2
• Extrahepatic connections (Types 1 and 2) carry significantly worse prognosis than intrahepatic connections (Type 3) 1, 6
• Among the two neonatal deaths in one series, both had extrahepatic absent ductus venosus 6

Outcomes Data

• In isolated cases (no other anomalies or aneuploidy), approximately 75-80% survive with appropriate management 1, 6
• When major anomalies or chromosomal aberrations are present, prognosis is substantially worse 1, 2
• Some fetuses with absent ductus venosus develop normally without significant circulatory disturbance, particularly with intrahepatic patterns 6

Critical Pitfalls to Avoid

• Do not assume isolated absent ductus venosus is benign—comprehensive evaluation for associated anomalies is mandatory given the 24% risk of major malformations 1
• Do not delay genetic testing, as chromosomal aberrations significantly impact prognosis and management 2
• Do not use ductus venosus Doppler for routine surveillance, as the vessel is absent; focus instead on cardiac function and hydrops monitoring 4, 7
• Do not fail to identify the specific pattern of venous circulation, as this critically determines prognosis and counseling 1, 3
• Do not deliver at a non-tertiary center, as these neonates require specialized cardiovascular and potentially surgical care 3