DIFFERENCES BETWEEN TWIN UMBILICAL COILING INDEXES CORRELATE TO DIFFERENCES IN TWIN WEIGHT AND DOPPLER INDEXES

Objective: The aim of our study was to evaluate sonographic and Dopple r detectable differences in umbilical coiling index and fetoplacental circulation of discordant twins. Study Design: Doppler blood now studi es in 13 pairs of concordant and 20 pairs of discordant twins were per formed from umbilical artery, middle cerebral artery, inferior vena ca va, and ductus venosus. Flow studies were compared and correlated with the antenatal sonographic coiling index and the actual umbilical cord length, number of vascular helices, and birth weight. All studies wer e performed within 72 h before delivery. Pulsatility index (PI) values were calculated for the arteries and preload index (PLI) values for t he veins. The umbilical coiling index (CI) was calculated using sonogr aphic longitudinal vie ws of cord vessels from several segments antena tally and by dividing the total number of helices by cord length (cm) postnatally. Discordancy was defined as a more than 20% intrapair actu al birth weight difference. For all these index values the intertwin d ifferences (a values) were calculated by subtracting the values obtain ed in the larger twin with those of the smaller twin. Results: The mea n +/- SD intertwin difference in umbilical coiling index was 27.4 +/- 10.5% in the antepartum period and 28.9 +/- 10.0% after birth, Regress ion analysis showed a significant linear trend (r = 0.77, P < 0.001) b etween intertwin birth weight difference (Delta BW) and intertwin coil ing index difference (Delta CI). A good correlation was found between Delta CI and Delta PLI in the ductus venosus (r = 0.63, P < 0.05), Del ta PLI in the inferior vena cava (r = 0.51, P < 0.005), and Delta PI i n the middle cerebral artery (r = 0.44, P < 0.05). Conclusions: Intert win difference in antepartum umbilical coiling index can be determined by ultrasound and con elates well with: 1) the actual difference in c oiling indices at birth, 2) the intertwin birth weight difference and 3) the intertwin Doppler flow characteristics in the fetal cerebral an d venous circulation.