Ultrasound evaluation of the size of the umbilical cord vessels and Wharton's jelly and correlation with intrapartum CTG findings.

Objective: To compare the sonographic measurement of the umbilical cord between women with or without repetitive decelerations during the first stage of labor.

Study Design: Prospective study including a non-consecutive cohort of women at term gestation carrying a normal sized fetus at term in cephalic presentation. The cross-sectional area of the umbilical cord, of its vessels and the amount of the Wharton's jelly were assessed at 2D ultrasound upon labor admission. The CTG traces recorded in labor were retrospectively evaluated and the biometric parameters of the umbilical cord were compared between women with or without repetitive decelerations during the first stage and their correlation with the total deceleration area/total length (stage I TDA/t) of the first stage of labor (overall and following the rupture of membrane) was assessed.

Results: Overall, 113 women were included, of whom 21 (18.6 %) presented repetitive decelerations during the first stage of labor. In this latter group, the umbilical cord showed a significantly smaller total arterial area (24.4 ± 10.7 vs. 19.6 ± 9.0 mm; p = 0.02), vein area (46.8 ± 13.6 vs. 34.1 ± 13.3 mm; p < 0.001) as well Wharton's Jelly (WJ) area (122.7 ± 32.1 vs. 79.3 ± 11.1 mm; p < 0.001) compared with fetuses with a normal CTG. At logistic regression analysis the WJ area was associated with the occurrence of repetitive decelerations during the first stage of labor (p < 0.001). The I stage TDA/t overall and after the rupture of membranes was found to be negatively correlated with the WJA (Spearman's coefficient -0.40; p < 0.001 and -0.45; p < 0.001 respectively).

Conclusion: In normal sized infants a reduced umbilical cord thickness is associated with an increased occurrence of repetitive decelerations during the first stage of labor. The severity of these decelerations is negatively correlated to the amount of WJ.