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.

Validation study of the capacity of the reference curves of ultrasonographic measurements of the umbilical cord to identify deviations in estimated fetal weight.

BACKGROUND: The objective of this study was to evaluate the capacity of the cross-sectional area and diameter of the umbilical cord, and the area of Wharton's jelly (WJ), to predict abnormalities in estimated fetal weight (EFW) in 20-40 week, low-risk pregnancies. METHODS: A validation study was performed in 1,828 pregnant women. Fetal weight was estimated by ultrasonography and classified as: small for gestational age (SGA), appropriate for gestational age (AGA) or large for gestational age (LGA) according to the 10th and 90th percentiles of the reference curve. Measurements of the parameters of the cord were used to classify it as thin, normal or thick using the 10th and 90th percentiles of the reference curves as limits. The capacity of the diameter and total area of the cord and the area of WJ to predict abnormal EFW was calculated for different gestational ages. RESULTS: The capacity of the diameter of thin cords to predict SGA fetuses (S =8.3%, PPV =16.5%) or thick cords to predict LGA fetuses (S =5.5%, PPV =30.1) was weak, similar to the capacity of the area of the umbilical cord to predict SGA (S =8.3%; PPV =16.3%) or LGA fetuses (S =5.5%; PPV =27.8%). The capacity of the area of WJ to predict SGA fetuses (S =5.7%, PPV =11.7%) was similar to its capacity to predict LGA fetuses (S =4%, PPV =27.1%). CONCLUSION: Despite the correlation between the diameter and cross-sectional area of the cord and EFW, these measurements were not found to be useful in predicting alterations in EFW and should not be used for this purpose.

Inter- and intra-observer variability in Sonographic measurements of the cross-sectional diameters and area of the umbilical cord and its vessels during pregnancy.

BACKGROUND: The purpose of the study was to evaluate inter- and intra-observer variability in sonographic measurements of the cross-sectional area of the umbilical cord and the diameters of its vessels in low-risk pregnancies of 12 to 40 weeks of gestation. METHODS: A prospective cross sectional study was performed in 221 pregnant women at different gestational ages. Measurements were carried out also by a second observer to evaluate inter-observer variability and repeated once again by the first observer to assess intra-observer variability. The linear correlation between the measurements (Spearman's coefficient of correlation) and their reliability through the intraclass correlation coefficient (ICC), the Cronbach's alpha coefficient and the limits of agreement proposed by Bland and Altman were evaluated. RESULTS: The results showed that inter-observer and intra-observer variability did not show any significant difference between examiners. A good linear correlation between the measurements and reliability was obtained, with values of R, ICC and Cronbach's alpha all above the standard limits. CONCLUSION: It is possible to conclude that inter- and intra-observer variability in the measurements of the umbilical cord and its vessels was small; their reliability and agreement were good.

Reference values for Doppler velocimetry of the ophthalmic and central retinal arteries in low-risk pregnancy.

OBJECTIVE: To establish reference values for Doppler velocimetry of the ophthalmic artery (OA) and the central retinal artery (CRA) in low-risk pregnancy. METHOD: Between January 2008 and March 2009, 63 low-risk pregnant women underwent an ultrasound scan every 2 weeks at the Women's Hospital, Campinas, Brazil, to determine the resistance index (RI), pulsatility index (PI), and peak systolic velocity of both arteries, in addition to the flow velocity of the second peak and peak ratio (PR) of the OA. For analysis, linear regression was used with mixed models for longitudinal data, coefficient of determination, and estimates of the 5th and 95th percentiles for each parameter at each gestational age. Intra- and inter-observer variability was evaluated via the intraclass correlation coefficient. RESULTS: There was a trend of a reduction with gestational age in PI and RI of the OA, and PI of the CRA, but not in PR of the OA; and the respective reference values were established. Intra- and inter-observer variability was considered satisfactory. CONCLUSION: Unilateral assessment of the orbital Doppler velocimetry is feasible. Establishment of reference values showed a negative correlation between gestational age and PI and RI of the OA, and PI of the CRA. The method demonstrated satisfactory reproducibility.