Intertwin discrepancy in middle cerebral artery peak systolic velocity and third-trimester fetal growth restriction in monochorionic–diamniotic twin pregnancy

Abstract

Objectives: To assess the role of intertwin discrepancy in middle cerebral artery peak systolic velocity (MCA-PSV) for the prediction of late selective intrauterine growth restriction (sIUGR) at birth and birth weight discrepancy of > 25% (BW-25) in otherwise uncomplicated monochorionic–diamniotic (MCDA) twin pregnancies. Methods: This was a cohort study including all MCDA pregnancies followed in a tertiary fetal medicine unit between 2008 and 2013. Exclusion criteria were referral after first trimester, abnormal karyotype, structural anomalies, twin-to-twin transfusion syndrome, twin anemia–polycythemia sequence and sIUGR detected before 28 weeks. MCA-PSV values of both twins measured in the second trimester (18–24 weeks) and early third trimester (26–32 weeks) were converted in multiples of the median (MoM). sIUGR was defined as birth weight < 5th centile. The relationship between MCA-PSV discrepancy, sIUGR and BW-25 was assessed by logistic regression analysis. Receiver–operating characteristics (ROC) curves were used to ascertain the predictive value of MCA-PSV discrepancy for such complications. Results: In total, 136 MCDA twin pregnancies were included in the analysis. Thirty (22.1%) were complicated with sIUGR at birth and 12 (8.8%) were complicated with BW-25. Logistic regression analysis identified MCA-PSV discrepancy as an independent predictor for sIUGR. ROC curves identified third-trimester MCA-PSV discrepancy as the best predictor for both sIUGR (area under ROC curve (AUC), 0.73 (95% CI, 0.62–0.85)) and BW-25 (AUC, 0.79 (95% CI, 0.65–0.93)). The optimal cut-off point for MCA-PSV discrepancy was 0.30 MoM (sensitivity, 70% and specificity, 69% for sIUGR; sensitivity, 83% and specificity, 72% for BW-25). Conclusion: In MCDA twin pregnancies, MCA-PSV discrepancy is associated with both sIUGR at birth and BW discordance.