Application of Umbilical Artery Classification in Complicated Monochorionic Twins

We report our experience on the application of Gratacos' classification in a cohort of monochorionic pregnancies complicated by selective intra-uterine growth retardation based on the Doppler assessment of the umbilical artery.

A retrospective study was conducted on 52 cases of monochorionic twin pregnancies, in which one twin presented an abdominal circumference at or below the 10th percentile for gestational age. Cases were classified into three types according to the umbilical artery Doppler in the smaller twin. Subsequently, patients were divided into two groups: the selective IntraUterine Growth Retardation group and the Twin-to-Twin Transfusion Syndrome (TTTS) group.

Of the total 52 cases, 37 were classified as Type I, 12 as Type II, and 3 as Type III cases. In the total group, progressive fetal deterioration of the smaller fetus requiring active management was observed in 66.7% of Type II and 11.1% of Type I cases (p < .001), and in no Type III case. Unexpected fetal death of the smaller twin was observed more frequently in Type III (two cases, 66.7%) than in Types I and II cases (5% and 33%, respectively). Among the 52 cases, TTTS with oligo-polyhydramnios sequence was diagnosed in 10 cases. The remaining 42 cases were therefore defined as selective intra-uterine growth retardation. In the selective IntraUterine Growth Retardation group, results were similar to those obtained for the whole population.

Classification of complicated monochorionic twins based on the umbilical artery Doppler is particularly important for counseling, even when we include TTTS cases, and permits the prediction of clinical evolution and perinatal outcome.