From the Guidelines
In single IUGR twin pregnancies, umbilical artery Doppler results are crucial for stratifying risk, with normal Doppler indicating lower risk, and absent or reversed end-diastolic flow indicating high or critical risk, respectively, guiding the frequency of monitoring and timing of delivery 1.
Risk Stratification
The risk stratification is based on the umbilical artery Doppler results, which can be categorized into three types:
- Normal umbilical artery Doppler, indicating lower risk, with monitoring recommended every 1-2 weeks
- Elevated resistance (increased pulsatility index), suggesting intermediate risk, requiring weekly surveillance
- Absent end-diastolic flow, representing high risk, necessitating monitoring 2-3 times weekly and consideration of delivery by 34 weeks
- Reversed end-diastolic flow, indicating critical risk, requiring daily or every-other-day monitoring and delivery consideration by 32 weeks or earlier depending on gestational age and clinical status
Management
The management of single IUGR twin pregnancies should occur in a center with appropriate neonatal facilities, as intervention timing balances risks of prematurity against continued intrauterine compromise.
- Antenatal corticosteroids should be administered if absent or reversed end-diastolic flow is noted at 34 weeks in a pregnancy with suspected IUGR 1
- Magnesium sulfate for neuroprotection should be considered if delivery is anticipated before 32 weeks
- Doppler assessment helps identify placental insufficiency severity and guides timing of antenatal corticosteroids, magnesium sulfate for neuroprotection, and optimal delivery timing
Key Considerations
- The affected twin faces increased risks of intrauterine demise, while the normally-growing co-twin may experience neurological injury if the compromised twin dies in utero
- The prognosis of the surviving twin is excellent when co-twin demise occurs early in pregnancy, but some studies have found a higher frequency of complications compared with singletons, including gestational diabetes, growth restriction, low birth weight, and perinatal mortality 1
From the Research
Stratification Risk in Single Intrauterine Growth Restriction (IUGR) Twin Pregnancies
The stratification risk in single IUGR twin pregnancies can be determined based on umbilical artery Doppler results.
- The risk of intrauterine fetal death (IUFD) is highest when the pregnancy is or becomes Type II reversed, with a hazard ratio (HR) of 9.5 [ 2 ].
- Type II absent umbilical artery Doppler flow is also associated with a higher risk of IUFD, with an HR of 4.3 [ 2 ].
- The outcome in monochorionic twins with selective IUGR and abnormal umbilical artery Doppler is poor under expectant management [ 3 ].
- Normal Doppler seems to be associated with a good prognosis [ 3 ].
Umbilical Artery Doppler Patterns
There are three clinical types of umbilical artery Doppler patterns in IUGR fetuses:
- Type I: normal umbilical artery Doppler and associated with good prognosis [ 4 ].
- Type II: persistently absent or reverse umbilical artery end-diastolic flow and associated with early deterioration of the IUGR twin and very preterm delivery [ 4 ].
- Type III: intermittently absent or reverse end-diastolic flow in the umbilical artery, and associated with unexpected fetal demise or neurological injury in one or both twins [ 4 ].
Management Strategies
Different prenatal management strategies, such as selective fetoscopic laser coagulation (SFLC), cord coagulation (CC), or expectant management, can impact the outcome of monochorionic twin pregnancies with selective IUGR and abnormal flow velocity waveforms in the umbilical artery Doppler [ 5 ].
- Expectant management seems to be a valid option when the estimated fetal weight (EFW) discordance is <30% and the a-wave in the ductus venosus (DV) is positive [ 5 ].
- Cord coagulation should be considered to protect the appropriately grown for gestational age (AGA) co-twin when the EFW discordance is ≥30% or the a-wave in DV is absent or negative [ 5 ].