The umbilical coiling index in complicated pregnancy.

OBJECTIVE: To evaluate umbilical cord coiling in pregnancies with adverse outcome. STUDY DESIGN: Umbilical cords and hospital records of 565 consecutive cases with an indication for histological examination of the placenta were studied. The umbilical coiling index (UCI) was determined as the number of complete coils divided by the length of the cord in centimeters, by an observer blinded for pregnancy outcome. Data on obstetric history and pregnancy outcome of each case were obtained from the hospital records. We calculated odds ratios and their 95% confidence interval to evaluate the strength of associations between pregnancy outcome and abnormal cord coiling. RESULTS: Fetal death (OR 4.09, 95% CI 2.22-7.55), chorioamnionitis (OR 1.77, 95% CI 1.09-2.88), fetal structural or chromosomal abnormalities (OR 1.78, 95% CI 1.08-2.95), and lower Apgar score at 5 min (p=0.03) were associated with undercoiling (UCI below the 10th percentile, using reference values from uncomplicated pregnancies). Fetal death (OR 3.74, 95% CI 1.89-7.40), iatrogenic preterm delivery (OR 1.91, 95% CI 1.04-3.49), umbilical arterial pH<7.05 (OR 3.63, 95% CI 1.44-9.17), fetal structural or chromosomal abnormalities (OR 1.79, 95% CI 1.01-3.16), thrombosis in fetal placental vessels (OR 2.64, 95% CI 1.37-5.06), chronic fetal hypoxia/ischemia (OR 1.82, 95% CI 1.09-3.05), and lower weight for gestational age (p=0.01) were associated with overcoiling (UCI above the 90th percentile). CONCLUSIONS: Our findings confirm that adverse perinatal outcome is associated with both undercoiling and overcoiling of the umbilical cord.

The umbilical coiling index, a review of the literature.

Our aim was to review the literature on umbilical cord coiling. Relevant articles in English published between 1966 and 2003 were retrieved by a Medline search and cross-referencing. The normal umbilical cord coiling index (UCI) is 0.17 (+/- 0.009) spirals completed per cm. Abnormal cord coiling, i.e. UCI <10th centile (<0.07) or >90th centile (>0.30) is associated with adverse pregnancy outcome. Hypocoiling of the cord is associated with increased incidence of fetal demise, intrapartum fetal heart rate decelerations, operative delivery for fetal distress, anatomic-karyotypic abnormalities and chorio-amnionitis. Hypercoiling of the cord is associated with increased incidence of fetal growth restriction, intrapartum fetal heart rate decelerations, vascular thrombosis and cord stenosis. It is not clear whether abnormal coiling is actually a cause of pathology, or merely one of the sequelae, or both. We discuss the theories involving the cause of cord coiling, and the consequences of the degree of cord coiling on blood flow through the umbilical vessels. In the future ultrasonographic evaluation of the umbilical cord and the UCI may become an integral part of fetal assessment in high-risk pregnancies.