What is the appropriate management for a 26‑year‑old woman at 29 weeks gestation (gravida 3, para 2) presenting with severe hypoxemia (SpO₂ 84% on supplemental oxygen), tachypnea, and echocardiography showing a moderate ventricular septal defect and a large atrial septal defect?

Emergency Management of Severe Hypoxemia in Pregnancy with Congenital Heart Disease

This 26-year-old pregnant woman at 29 weeks with severe hypoxemia (SpO₂ 84% on oxygen), moderate VSD, and large ASD requires immediate hospitalization in a tertiary center with maternal-fetal medicine and adult congenital heart disease expertise, urgent echocardiographic assessment of pulmonary artery pressures to rule out pulmonary hypertension or Eisenmenger physiology, and consideration of pregnancy termination if pulmonary hypertension is confirmed, as maternal mortality exceeds 30-50% in this scenario. 1

Immediate Diagnostic Priorities

Rule Out Pulmonary Hypertension

• Urgent transthoracic echocardiography with Doppler estimation of pulmonary artery pressures is mandatory to determine if this patient has developed pulmonary arterial hypertension (PAH) or Eisenmenger physiology, which would explain the severe hypoxemia through right-to-left shunting. 1
• Measure tricuspid regurgitation jet velocity and pulmonary regurgitation velocity with simultaneous systemic blood pressure measurement to calculate pulmonary artery pressures. 1
• Assess for evidence of right ventricular dysfunction, which can precipitate right-to-left shunting through the ASD even without fixed pulmonary hypertension. 2, 3

Determine Shunt Direction

• The combination of large ASD and moderate VSD can produce bidirectional or predominantly right-to-left shunting if right heart pressures exceed left heart pressures, explaining the profound hypoxemia. 1, 4
• Bubble contrast echocardiography should be performed to document the presence and timing of right-to-left shunting across the ASD. 1
• Normal right heart pressures with severe hypoxemia would suggest anatomic factors directing inferior vena caval blood preferentially into the left atrium through the ASD. 4

Risk Stratification

High-Risk Scenarios (WHO Class IV)

• If mean pulmonary artery pressure exceeds 25 mmHg or any degree of pulmonary hypertension is confirmed, maternal mortality risk is 30-50% and pregnancy termination should be strongly recommended. 1
• Eisenmenger physiology (pulmonary hypertension with right-to-left shunting and cyanosis) carries maternal mortality of 20-50%, with most deaths occurring in the third trimester or early postpartum period. 1
• Even moderate forms of pulmonary vascular disease can worsen during pregnancy due to decreased systemic vascular resistance and right ventricular overload. 1

Potentially Manageable Scenarios

• If pulmonary artery pressures are normal and hypoxemia is due to anatomic shunt direction without pulmonary hypertension, continuation of pregnancy may be considered with intensive monitoring, though this remains high-risk. 1, 5
• Large ASDs with significant left-to-right shunting but no pulmonary hypertension are generally well tolerated in pregnancy (WHO Class II-III), but severe hypoxemia at 29 weeks suggests this is not the case here. 1, 6

Acute Management

Oxygen and Hemodynamic Support

• Administer supplemental oxygen to maintain SpO₂ >90% if possible, recognizing that refractory hypoxemia despite high-flow oxygen suggests significant right-to-left shunting. 1, 7
• Avoid systemic hypotension, which increases right-to-left shunting by decreasing left atrial pressure relative to right atrial pressure. 1, 2
• Maintain adequate circulating volume, as hypovolemia worsens right-to-left shunting and can precipitate cardiovascular collapse. 1

Avoid Triggers for Pulmonary Hypertensive Crisis

• Avoid hypoxia, acidosis, hypercarbia, and hypothermia, all of which increase pulmonary vascular resistance and worsen right-to-left shunting. 1
• Minimize anxiety and pain, which can trigger pulmonary hypertensive crises. 1

Pregnancy Continuation vs. Termination

Strong Indications for Termination

• Confirmed pulmonary hypertension of any severity is an absolute contraindication to pregnancy continuation due to prohibitive maternal mortality risk. 1
• Eisenmenger physiology with cyanosis and right-to-left shunting mandates pregnancy termination. 1
• Termination should be performed in a tertiary center experienced in managing PAH patients, as anesthesia itself carries significant risk. 1

If Pregnancy Continues Despite Risk

• If the patient refuses termination despite confirmed pulmonary hypertension, she must be managed in a center with expertise in PAH with all therapeutic options available. 1
• Consider intravenous prostacyclin or aerosolized iloprost to improve hemodynamics, though evidence in pregnancy is limited to case reports. 1
• Anticoagulation with subcutaneous low-molecular-weight heparin or unfractionated heparin should be considered if pulmonary artery thrombosis or heart failure is present. 1

Fetal Considerations

Impact of Maternal Cyanosis

• Maternal cyanosis poses significant risk to the fetus, with neonatal survival rates of only 87-89% in mothers with pulmonary hypertension. 1
• There is an increased incidence of intrauterine growth restriction and congenital anomalies in infants born to mothers with cyanotic heart disease. 1
• At 29 weeks gestation, fetal viability is marginal, and maternal survival must take priority. 1

Delivery Planning (If Pregnancy Continues)

Timing and Mode

• Cesarean delivery is contraindicated in pulmonary hypertension due to the hemodynamic stress of surgery and anesthesia; vaginal delivery with assisted second stage is preferred if delivery becomes necessary. 8
• Emergency cesarean delivery carries higher risk than planned vaginal delivery in cardiac patients. 8
• If maternal condition deteriorates, early delivery may be necessary despite prematurity, but this decision must balance maternal survival against fetal viability. 1

Anesthesia Considerations

• General anesthesia is a risk factor for maternal death in pulmonary hypertension and should be avoided if possible. 1
• Regional anesthesia can cause systemic vasodilation that increases right-to-left shunting and must be used with extreme caution. 5

Critical Pitfalls to Avoid

• Do not assume this is "just" an ASD and VSD without pulmonary hypertension—the severe hypoxemia at 29 weeks strongly suggests either pulmonary hypertension or significant right-to-left shunting. 1
• Do not delay echocardiographic assessment of pulmonary pressures, as this is the single most important prognostic factor. 1
• Do not underestimate the risk of sudden deterioration in the peripartum and early postpartum period, when most maternal deaths occur. 1
• Do not manage this patient in a community hospital—transfer to a tertiary center with adult congenital heart disease and high-risk obstetric expertise is mandatory. 8
• Do not use pulmonary artery catheterization for hemodynamic monitoring, as it is associated with serious complications including pulmonary artery rupture in PAH patients. 1