How should a dichorionic-diamniotic (DCDA) twin pregnancy be managed?

Management of Dichorionic-Diamniotic (DCDA) Twin Pregnancy

DCDA twin pregnancies require ultrasound surveillance every 3-4 weeks starting after the anatomy scan, with transabdominal ultrasound for growth monitoring and Doppler studies reserved for cases with growth discordance, while delivery should occur at 38-39 weeks in uncomplicated cases. 1, 2

Initial Assessment and Chorionicity Determination

• Establish chorionicity and amnionicity in the first trimester using both transabdominal and transvaginal ultrasound, as this is the most accurate time for determination and fundamentally guides all subsequent management 1, 2
• DCDA twins have significantly lower complication rates than monochorionic twins (10% overall mortality in monochorionic vs. much lower in dichorionic), but still require more intensive monitoring than singleton pregnancies 2

Routine Surveillance Protocol

Ultrasound Frequency

• Perform transabdominal ultrasound every 3-4 weeks for uncomplicated DCDA twins beginning after the anatomy scan 1, 2
• Increase surveillance frequency if growth discordance, oligohydramnios, or other complications develop 1, 2

Parameters to Assess at Each Visit

• Fetal biometry for both twins to calculate estimated fetal weight (EFW) 1
• Amniotic fluid volume assessment for both sacs 1
• Calculate and document EFW discordancy at each scan from 20 weeks onward, with growth discordance defined as mild (15% difference), moderate (20%), or severe (≥25%) 1, 2
• Umbilical artery Doppler studies after 20 weeks when growth discrepancy is identified 1

Anatomy Scan Considerations

• Perform detailed anatomic survey with transabdominal ultrasound at 18-22 weeks 1
• Evaluate placenta, umbilical cords, and cervix for placenta previa, marginal or velamentous cord insertion 1
• Consider fetal echocardiography for twins conceived via IVF due to increased risk of congenital heart disease 1
• Perform transvaginal cervical length assessment to stratify preterm delivery risk, with cervical length <1.5cm being highly predictive of preterm labor 1, 2

Management of Complications

Growth Discordance

• Initiate umbilical artery Doppler velocimetry when growth discrepancy is detected, as there is no proven benefit in uncomplicated twins but it is helpful when growth delay is suspected 1
• DCDA pregnancies with selective fetal growth restriction have 5.2-fold increased risk of intrauterine death and 3.2-fold increased risk of composite neonatal morbidity compared to uncomplicated DCDA twins 3
• Increase surveillance frequency and consider antenatal testing (nonstress test or biophysical profile) for pregnancies with growth abnormalities 1

Preeclampsia

• DCDA twins with preeclampsia without severe features have optimal outcomes when delivered at 36 weeks, balancing maternal risks (severe preeclampsia, stroke, mortality) against neonatal risks (cerebral palsy, neonatal mortality) 4
• Preeclampsia or gestational hypertension complicates approximately 20% of DCDA pregnancies with selective growth restriction versus 13% without 3

Single Fetal Demise

• The prognosis for the surviving twin is generally excellent, especially with early demise, as DCDA twins do not share placental circulation 5
• Continue surveillance every 3-4 weeks with fetal biometry, amniotic fluid assessment, and umbilical artery Doppler 5
• Deliver at 39 weeks if no other complications develop 5
• Administer RhoGAM to Rh-negative women to prevent alloimmunization 5

Antenatal Testing

• Nonstress testing or biophysical profile is reliable in DCDA twins when indicated by standard obstetric criteria: abnormal fluid volumes, pregnancy-induced hypertension, fetal anomalies, growth abnormalities 1
• There is no proven benefit of routine biophysical profile in uncomplicated DCDA twin pregnancies 2

Delivery Timing

• Deliver uncomplicated DCDA twin pregnancies at 38-39 weeks to optimize outcomes 5
• Consider delivery at 36 weeks for preeclampsia without severe features based on decision analysis showing optimal quality-adjusted life years 4
• Earlier delivery is indicated for abnormal Doppler findings, severe growth restriction, or maternal complications 5

Common Pitfalls to Avoid

• Do not perform routine umbilical artery Doppler in uncomplicated DCDA twins, as there is no proven benefit; reserve for cases with suspected growth delay 1
• Do not use singleton growth charts; growth discordance calculations are twin-specific and critical for management 1, 2
• Do not overlook cervical length assessment, as short cervix significantly increases preterm delivery risk and may warrant intervention 1, 2
• Do not assume both twins require the same level of concern; in growth-restricted pairs, the smaller twin has 2.1-fold higher perinatal death risk and 1.9-fold higher composite morbidity risk compared to the appropriately grown co-twin 3