Variation of the maximum velocity along the umbilical vein supports the Reynolds pulsometer model.

OBJECTIVE: To challenge, with a modern sonographic approach and a numerical model, the Reynolds's concept which suggests that the vascular structure of the umbilical cord could act as a pulsometer facilitating the venous return to the foetus. METHOD: Forty-five patients between 20 and 28 weeks of gestation were included in the study. The blood maximum velocity in the umbilical vein, measured at both foetal and placental ends, was assessed. Several sonographic parameters of the cord, including the diameter of the umbilical vein at both extremities, cord cross-sectional area and Wharton's jelly section surface were measured. We compare our data with those of a numerical model. RESULTS: A difference in maximum velocity between the two extremities of the umbilical vein (ΔUVVmax) was noted. The maximum velocity was significantly higher at the foetal umbilical end (14.12 +/-3.18 cm/s) than at the placental end (11.93 +/-2.55 cm/s; p < 0.0001). The mean difference is 2.2 +/- 2.3 cm/s. No difference in the umbilical vein diameter was measured at both cord ends (umbilical 4.85 +/-0.9 mm, placental 4.86 +/-0.87 mm, p < 0.0001). There is no significant relationship between ΔUVVmax and the cord cross-sectional area or Wharton's jelly index. CONCLUSION: Modifications of the spatial velocity profile together with the pulsometer model could explain the maximum velocity changes that is measured in the umbilical vein along the cord. This numerical model consolidates the sonographic observations.

Longitudinal reference range for umbilical cord cross-sectional area in twin pregnancies at 18-32 weeks of gestation.

OBJECTIVES: The objectives of this study were to establish gestational age-specific reference ranges for cross-sectional area of the umbilical cord, and its components, in twin pregnancies and to compare them with previously reported singleton reference ranges. METHODS: This was a prospective longitudinal study involving uncomplicated dichorionic twin pregnancies. Sonographic measurements of the cross-sectional area of the umbilical cord, umbilical vein and arteries and Wharton's jelly were obtained in a plane adjacent to the fetal abdomen, every 3 weeks, between 18 and 32 weeks of gestations. Multilevel regression analysis was used to determine gestational age-specific reference ranges for each parameter, and these were plotted against singleton pregnancy references. RESULTS: Three hundred and thirty four ultrasound scans were performed in 44 twin pregnancies, between 18 and 32.9 weeks (mean: 3.8 ± 0.7 scans/pregnancy and mean interval between scans: 3.3 ± 0.9 weeks). All umbilical cord cross-sectional areas (total, vein, artery and Wharton's jelly) showed a significant increase with gestational age. Compared with singleton pregnancy ranges, mean values were considerably lower in twin pregnancies and resemble the lower limits observed in singletons. CONCLUSION: In twin pregnancies, cross-sectional area of the umbilical cord, and its components, increases between 18 and 32 weeks, and mean values are substantially lower compared with singleton pregnancies.

The role of umbilical cord thickness and HbA1c levels for the prediction of fetal macrosomia in patients with gestational diabetes mellitus.

OBJECTIVE: The aim of this study was to investigate the effects of HbA1c levels and umbilical cord thickness upon birth weight, particularly in pregestational and gestational diabetic patients. METHOD: Pregnant women were included in the study and were divided into two groups. The first group consisted of patients who were diagnosed with pregestational or gestational diabetes mellitus. The control group consisted of pregnant women who were not diagnosed with pregestational or gestational diabetes mellitus. Ultrasound examination was performed twice. Examinations were performed at 27-28 weeks and 36-37 weeks of gestation, respectively. During ultrasound examinations, fetal anthropometric parameters, biparietal diameter, abdominal circumference, femur length and estimated fetal weight (which was calculated automatically according to Hadlock's formula) were measured. Additionally, the sonographic cross-sectional areas of the umbilical cord, the umbilical arteries and the umbilical vein were measured in a free loop of the umbilical cord, using the software of the ultrasound machine. The cross-sectional area of Wharton's jelly was computed by subtracting the cross-sectional area of the vessels from that of the umbilical cord. HbA1c levels were measured for diabetic patients. RESULTS: At 27-28 gestational weeks, umbilical cord area and Wharton's jelly values were found to be statistically different in macrosomic fetuses compared with non-macrosomic fetuses for both groups (for cord area, P = 0.012; for Wharton's jelly, P = 0.001). Additionally, umbilical cord diameter vein and artery values were not statistically different between the two groups when macrosomic fetuses were compared with non-macrosomic fetuses. At 36-37 gestational weeks, when the relationship between umbilical cord components and birth weight was examined, there was a statistically significant difference when comparing macrosomic fetuses with non-macrosomic fetuses. There was a statistically significant correlation between umbilical cord area, umbilical cord diameter and fetal weight estimation at 36-37 gestational weeks. HbA1c values and fetal macrosomia did not show a statistically significant relationship (P = 0.701). CONCLUSION: A significant relationship between umbilical cord components and birth weight was not specific for the diabetic group. There was a significant relationship between birth weight and umbilical cord components for the control group as well. If the estimated fetal weight is combined with umbilical cord components, macrosomic fetuses can be predicted with more accuracy.

Area of Wharton's jelly as an estimate of the thickness of the umbilical cord and its relationship with estimated fetal weight.

BACKGROUND: To build a reference curve for the area of Wharton's jelly (WJ) in low-risk pregnancies from 13 to 40 weeks and to assess its relationship with estimated fetal weight (EFW). METHODS: 2,189 low-risk pregnancies had the area of WJ estimated by ultrasound and the 10th, 50th and 90th percentiles calculated using a third-degree polynomial regression procedure. EFW by ultrasound was correlated with the measurement of the area of WJ. RESULTS: The area of WJ increased according to gestational age (R² = 0.64), stabilizing from the 32nd week onwards. There was a significant linear correlation between area of WJ and EFW up to 26 weeks (R = 0.782) and after that 5t remained practically constant (R = 0.047). CONCLUSION: The area of WJ increases according to gestational age, with a trend to stabilize at around 32 weeks of gestation. It is also linearly correlated with EFW only up to 26 weeks of gestation.