Prognostic performance of umbilical artery Doppler-based classification in monochorionic pregnancies complicated by...

To evaluate the performance of the umbilical artery (UA) Doppler-based classification system, published by Gratacós et al., in stratifying selective fetal growth restriction (sFGR) by severity and predicting adverse outcomes in affected monochorionic diamniotic (MCDA) pregnancies.

This was a retrospective cohort study of MCDA pregnancies complicated by sFGR, seen at a single tertiary center (St George's Hospital, London, UK) from January 2000 to July 2024. Included cases were diagnosed with sFGR using the criteria of the recent Delphi consensus. Fetal growth was evaluated using twin-specific charts. A comparison of perinatal outcomes across the different groups of sFGR severity according to the UA Doppler-based classification was performed. Additionally, the discriminatory performance of this classification system and other ultrasound parameters for adverse outcomes was investigated using receiver-operating-characteristics (ROC)-curve analysis.

Overall, 107 pregnancies complicated by sFGR were included in the analysis. The majority of cases were classified as Type-I sFGR (83/107 (77.6%)) as per the UA Doppler-based classification, while 15.0% (16/107) of cases were Type II and 7.5% (8/107) were Type III. Superimposed twin-twin transfusion syndrome occurred in 6.0% of Type-I sFGR, 18.8% of Type-II sFGR and 37.5% of Type-III sFGR cases (P = 0.010). The rate of intact survival of both twins without perinatal complications was found to be significantly higher in Type-I cases (54.2%) than in Type-II cases (18.8%) (P = 0.013). No significant differences were found in the rates of double intrauterine fetal demise (IUFD), IUFD of the smaller twin or composite adverse perinatal outcome (CAPO) of either twin. The discriminatory performance of the UA Doppler-based sFGR classification at diagnosis for predicting the occurrence of CAPO in the smaller twin was low (area under the ROC curve (AUC), 0.615 (95% CI, 0.506-0.723)). The combination of severity classification using the UA Doppler-based system with other variables (early diagnosis of sFGR, fetal weight discordance (%) and estimated fetal weight of one twin < 3^rd centile) in different models adjusted for gestational age at delivery, laser photocoagulation and classification stage progression showed good discriminatory performance for predicting CAPO in the smaller twin (AUC > 0.9 for all).

The UA Doppler-based sFGR classification has limited value in predicting adverse outcomes in pregnancies complicated by sFGR. The combination of severity classification using the UA Doppler-based system with other variables could improve the discriminatory performance and therefore its value in clinical practice. Larger studies are needed to investigate the optimal predictive tool to assess severity in monochorionic pregnancies complicated by sFGR. © 2026 International Society of Ultrasound in Obstetrics and Gynecology.