What is the management approach for a dichorionic diamniotic (Di-Di) twin pregnancy when one fetus is not viable?

Management of Dichorionic Diamniotic Twin Pregnancy with One Non-Viable Fetus

In a dichorionic diamniotic (Di-Di) twin pregnancy with one non-viable fetus, expectant management with continued surveillance of the surviving twin is recommended, as the separate placental circulations eliminate the risk of acute hemodynamic compromise to the co-twin, and delivery timing should be based on the condition of the surviving twin rather than the demised fetus. 1

Risk Assessment and Prognosis

The prognosis for the surviving twin in dichorionic pregnancies is generally excellent, particularly when demise occurs early in pregnancy (first trimester). 1 Unlike monochorionic twins, dichorionic twins do not share placental circulation, which significantly reduces the risk of neurological injury or acute hemodynamic instability to the surviving twin following co-twin demise. 1

However, the surviving twin remains at higher risk compared to singletons for:

• Growth restriction 1
• Low birth weight 1
• Preterm delivery 1

Surveillance Protocol

Ultrasound Monitoring

• Perform ultrasound assessments every 3-4 weeks for dichorionic twins without additional complications. 2, 1
• Each scan should include:
  • Fetal biometry to monitor growth 1
  • Amniotic fluid volume assessment 1
  • Umbilical artery Doppler studies after 20 weeks of gestation 1

Cervical Assessment

• Transvaginal ultrasound for cervical length should be performed to evaluate preterm delivery risk, as this helps triage patients into higher-risk groups. 2, 1

Growth Monitoring

• Calculate and document estimated fetal weight (EFW) at each scan from 20 weeks onward, comparing to standard growth charts. 1
• Monitor for selective intrauterine growth restriction (sIUGR), defined as EFW below the 10th percentile. 1
• Abdominal circumference discordance greater than 10% between 14-22 weeks is a predictor of subsequent adverse outcomes and warrants closer surveillance. 1

Intensified Surveillance Triggers

• Increase surveillance frequency if signs of growth restriction, abnormal Doppler findings, or other complications develop. 1

Delivery Timing

With no other obstetric complications, dichorionic pregnancies with previous single fetal demise can be delivered at term (39 weeks of gestation). 1 This recommendation prioritizes avoiding complications of prematurity in the surviving twin. 2

Earlier Delivery Indications

Consider delivery before 39 weeks if:

• Abnormal umbilical artery Doppler findings develop (absent or reversed end-diastolic flow) 2, 1
• Growth restriction of the surviving twin is identified 1
• Maternal complications arise (hypertension, preeclampsia) 1

Additional Management Considerations

Rh Immunization Prevention

• Administer Rh immunoglobulin (RhoGAM) to Rh-negative women to prevent alloimmunization. 1

Documentation and Counseling

• Document the confirmed fetal demise with ultrasound findings. 1
• Counsel the patient regarding expectations about the retained demised fetus, which will typically remain in utero until delivery without causing harm to the surviving twin. 1

Common Pitfalls to Avoid

• Do not deliver prematurely based solely on the presence of the demised twin. The separate placental circulations in dichorionic pregnancies mean there is no acute risk to the surviving twin from the demised co-twin. 1
• Do not assume the surviving twin will develop normally without surveillance. Continue regular monitoring as the surviving twin has increased risks compared to singletons. 1
• Do not rely solely on biophysical profile or amniotic fluid volume for surveillance. Umbilical artery Doppler and growth assessment are the primary surveillance modalities. 2, 1