Does Doppler Classification Accurately Predict sFGR?

Managing twin pregnancies requires precise risk stratification, particularly when managing selective fetal growth restriction in monochorionic diamniotic gestations. Clinicians frequently rely on the Gratacós umbilical artery Doppler classification system to guide counseling and surveillance. However, a recent retrospective cohort study from St George's Hospital in London critically evaluated whether this classification alone adequately predicts composite adverse perinatal outcomes.

Evaluating Selective Fetal Growth Restriction Severity

The study reviewed 107 monochorionic diamniotic pregnancies complicated by growth discordance. Researchers classified each case at diagnosis using umbilical artery Doppler waveform patterns into Type I, Type II, or Type III. Consequently, the team tracked rates of twin-twin transfusion syndrome, intrauterine fetal demise, and intact survival without morbidity.

Overall, Type I cases represented 77.6% of the cohort, while Type II accounted for 15.0% and Type III accounted for 7.5%. Furthermore, superimposed twin-twin transfusion syndrome occurred significantly more often in Type III (37.5%) and Type II (18.8%) cases compared to Type I cases (6.0%). Additionally, intact survival of both infants was markedly higher in Type I cases (54.2%) than in Type II cases (18.8%).

Limitations of Doppler Stratification in Clinical Practice

Despite clear survival differences between subtypes, the standalone Doppler classification demonstrated low discriminatory performance for predicting composite adverse perinatal outcomes in the growth-restricted twin, yielding an area under the curve of only 0.615. Therefore, relying solely on umbilical artery Doppler waveforms may leave critical clinical blind spots.

In contrast, combining the Doppler staging with earlier gestational age at diagnosis, severe inter-twin weight discordance, and low estimated fetal weight markedly improved prognostic accuracy. Thus, multiparametric models offer substantially better risk assessment for clinicians specializing in fetal medicine caring for complicated monochorionic pregnancies.

Frequently Asked Questions

Q1: What are the three Doppler types of selective fetal growth restriction?

Type I shows positive end-diastolic flow in the umbilical artery. Type II exhibits persistently absent or reversed end-diastolic flow, whereas Type III demonstrates intermittent absent or reversed end-diastolic flow.

Q2: Why does standalone Doppler classification show limited predictive accuracy?

Umbilical artery Doppler reflects downstream placental vascular resistance, but it does not capture the full hemodynamic impact of placental sharing discordance or early disease onset without combining other biometric variables.

Q3: Which additional ultrasound parameters improve prognostic performance?

Incorporating gestational age at diagnosis, percentage of fetal weight discordance, and severely reduced estimated fetal weight significantly enhances predictive power for adverse perinatal outcomes.

References

1. Sorrenti S et al. Prognostic performance of umbilical artery Doppler-based classification in monochorionic pregnancies complicated by selective fetal growth restriction. Ultrasound Obstet Gynecol. 2026 Aug 29. doi: 10.1002/uog.70320. PMID: 42667608.
2. Gratacós E, Lewi L, Muñoz B, Acosta-Rojas R, Hernandez-Andrade E, Martinez JM, Carreras E, Deprest J. A classification system for selective intrauterine growth restriction in monochorionic pregnancies according to umbilical artery Doppler flow in the smaller twin. Ultrasound Obstet Gynecol. 2007 Jul;30(1):28-34. doi: 10.1002/uog.4046.
3. Khalil A, Sotiriadis A, Baschat A, et al. ISUOG Practice Guidelines (updated): role of ultrasound in twin pregnancy. Ultrasound Obstet Gynecol. 2025 Feb;65(2):253-276. doi: 10.1002/uog.29166.