Inter-twin discrepancy in middle cerebral artery peak systolic velocity and pregnancy outcome in monochorionic diamniotic twin pregnancies

OBJECTIVES: To assess the role of inter-twin 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 (BW) discrepancy >25% (BW-25) in otherwise uncomplicated monochorionic diamniotic (MCDA) twin pregnancies. METHODS: Cohort study on all MCDA pregnancies followed in a tertiary fetal medicine unit between 2008-2012.EXCLUSION CRITERIA: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 characteristic (ROC) curves were used to ascertain the predictive value of MCA-PSV discrepancy for such complications. RESULTS: 136 MCDA twin pregnancies were included in the analysis. Thirty (22.1%) were complicated with sIUGR at birth; 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 (AUC 0.73; 95%Cl 0.62-0.85; p < 0.001) and BW-25 (AUC 0,79; 95% Cl 0,65 - 0,93). The optimal cut off point was 0.30 MoM (sensitivity 0.67, specificity 0.76 for sIUGR; sensitivity 0.83, specificity 0.72 for BW-25). CONCLUSION: In MCDA twin pregnancies, MCA-PSV discrepancy is related to both sIUGR at birth and BW discrepancy..