Monochorionic twin pregnancies present significant risks. Clinicians must identify effective methods to predict adverse perinatal events. Therefore, a new multicentre cohort study investigated how combining estimated fetal weight (EFW) discordance with fetal Doppler data predicts monochorionic twin outcome.
The study was a retrospective analysis of 624 monochorionic twin pregnancies. These cases were managed across three tertiary centers between 2013 and 2023. The main adverse outcomes assessed were stillbirth or iatrogenic preterm birth before 34 weeks for suspected fetal compromise. Overall, the primary outcome occurred in 22.9% of the pregnancies. This included 70 cases of early preterm birth and 73 cases of at least one intrauterine death (IUD). Significant associations between biometric and Doppler parameters and the adverse outcomes were found.
EFW and Doppler Discordance Predict Monochorionic Twin Outcome
The study demonstrated that the best-performing prediction models incorporated a combination of ultrasound measures. Specifically, the best model included EFW discordance and umbilical artery pulsatility index (UA PI) discordance. This model achieved a high area under the curve (AUC) of 0.85. Furthermore, a second high-performing model used EFW discordance alongside absent or reverse end-diastolic flow in the UA PI, achieving an AUC of 0.86. The research indicates that EFW discordance plus UA PI discordance can be applied to a larger proportion of twin pregnancies. Consequently, this combined model outperformed the currently used clinical classification for selective fetal growth restriction (sFGR) in predicting poor outcomes.
In fact, current consensus guidelines strongly recommend regular fetal Doppler assessment in monochorionic twins every two weeks starting from 16 weeks’ gestation. This surveillance includes assessing the umbilical artery, middle cerebral artery, and ductus venosus. Abnormal Doppler findings, such as those related to the umbilical artery, are established indicators of compromised fetal circulation. Moreover, EFW discordance exceeding 20% to 25% is widely recognised as a significant independent risk factor for poor perinatal outcomes, including preterm delivery and IUGR. Therefore, integrating these two crucial markers into one tailored model offers a major clinical advantage for timely intervention.
This new prediction model could greatly contribute to a more tailored risk assessment. Ultimately, this approach will help optimise the timing of birth in these complex pregnancies. However, the authors stress the need for further external validation studies to confirm the generalizability of these findings before widespread clinical implementation.
Frequently Asked Questions
Q1: What specific parameters improved the prediction model?
The most effective models combined intertwin estimated fetal weight (EFW) discordance with umbilical artery pulsatility index (UA PI) discordance. The presence of absent or reverse end-diastolic flow in the UA PI also formed a highly accurate model.
Q2: Why is a new model needed for monochorionic twins?
Monochorionic twin pregnancies carry a high risk of unique complications, such as twin-to-twin transfusion syndrome (TTTS) and selective fetal growth restriction (sFGR). The study showed that the new combined model significantly outperformed the current clinical sFGR classification in predicting adverse perinatal monochorionic twin outcomes, thus allowing for better timing of delivery.
Q3: What are the main adverse perinatal outcomes addressed by this study?
The study focused on stillbirth at any gestation and iatrogenic preterm birth (delivery before 34 weeks) initiated due to suspected fetal compromise.
References
- Lopian M et al. Prediction of Adverse Perinatal Outcome in Monochorionic Twin Pregnancy Using Fetal Biometry and Doppler Data: A Multicentre Cohort Study. BJOG. 2025 Dec 16. doi: 10.1111/1471-0528.70116. PMID: 41402970.
- Doppler assessment in twin pregnancies. International Society of Ultrasound in Obstetrics and Gynaecology (ISUOG).
- Fetal Doppler in monochorionic pregnancies complicated by twin-to-twin transfusion syndrome and selective in utero growth restriction. Eur J Obstet Gynecol Reprod Biol. 2023 Apr.
- Weight discordance in monochorionic and dichorionic twins: a cohort study. Am J Obstet Gynecol. 228(1): 114.e1-114.e11. 2023 Jan.