Umbilical Venous Diameter Research Articles

Intra-abdominal umbilical venous diameter and abdominal circumference discordance at 15-20weeks' gestation: simple markers in transverse abdominal plane to predict adverse pregnancy outcomes in monochorionic diamniotic twins.

This study aimed to investigate the association between simple markers in fetal abdominal plane, intra-abdominal umbilical venous diameter (DIUV) and abdominal circumference (AC) discordance at 15-20weeks' gestation, and adverse pregnancy outcomes in monochorionic diamniotic (MCDA) twins. We performed a retrospective analysis of MCDA twins with two live fetuses examined at 15-20weeks from Jun 2020 to Dec 2021 at Beijing Obstetrics and Gynecology Hospital. Measurement of fetal AC and DIUV was performed according to standard protocols. Twin pregnancies with major fetal structural anomalies, chromosomal abnormalities, miscarriage, and twin reversed arterial perfusion sequence were excluded. DIUV and AC discordance in MCDA twins with an adverse pregnancy outcome was compared with a normal pregnancy outcome. Furthermore, the performance of DIUV and AC discordance in predicting adverse pregnancy outcomes in MCDA twins was assessed. A total of 105 women with MCDA twin pregnancies were enrolled, contributing 179 visits. Adverse pregnancy outcomes occurred in 33.3% (35/105) of cases in our study. The intra-observer and inter-observer intraclass correlation coefficient (ICC) of both AC and DIUV were very good or excellent. There was no statistical difference in AC and DIUV discordance (%) between 15-16, 17-18, and 19-20weeks (χ2 = 3.928, P = 0.140; χ2 = 2.840, P = 0.242). Both AC and DIUV discordance were greater in twins with adverse pregnancy outcomes than that in twins with normal pregnancy outcome at each pregnancy periods. Both AC discordance (OR 1.2, 95% CI 1.1-1.3) and DIUV discordance (OR 1.2, 95% CI 1.1-1.2) were associated with adverse pregnancy outcomes. The AUC for predicting adverse pregnancy outcomes by AC discordance was 0.75 (95% CI 0.68-0.83), with a sensitivity of 58.7% (95% CI 51.9-64.5) and a specificity of 86.2% (95% CI 81.7-88.4). The AUC for predicting adverse pregnancy outcomes by DIUV was 0.78 (95% CI 0.70-0.86), with sensitivity and specificity of 65.1% (95% CI 58.1-70.3) and 86.2% (95% CI 81.7-88.4), respectively. The AC discordance and DIUV discordance could predict adverse pregnancy outcomes in MCDA twins. When these simple markers occurred, intensive surveillance was recommended.

Does umbilical venous diameter or time-averaged maximum velocity correlate better with fetal outcome in growth-restriction?

Does umbilical venous diameter or time-averaged maximum velocity correlate better with fetal outcome in growth-restriction?

Umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy: association with placental sharing and fetal demise.

To examine the association of umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy with placental sharing and fetal demise. This was a prospective longitudinal cohort study of a consecutive series of monochorionic diamniotic twin pregnancies that underwent ultrasound assessments at 12, 16, 20 and 28 weeks' gestation. Fetal biometry (crown-rump length at 12 weeks or estimated fetal weight (EFW) thereafter) and cord insertion sites were recorded at each visit, as well as the diameter of the umbilical vein (UV) in both the intra-abdominal part and a free loop of the umbilical cord. Time-averaged maximum velocity in the intra-abdominal part of the UV was measured to calculate UV-flow. Univariate and multivariate linear regression analyses were performed to assess the relationship between intertwin ratios of these variables and placental sharing at 12, 16, 20 and 28 weeks' gestation. Placental sharing was calculated by dividing the larger by the smaller placental share, as measured on placental injection studies after birth. Additionally, the Mann-Whitney U-test and receiver-operating-characteristics-curve analysis were used to explore the relationship between the occurrence of fetal demise and intertwin differences in fetal biometry, cord insertion sites, UV diameters and flow at 12, 16, 20 and 28 weeks. Of 200 consecutive monochorionic twin pregnancies enrolled, injection studies were performed in 165 (82.5%) placentas. On univariate analysis, intertwin differences in fetal biometry, cord insertions and UV variables were associated significantly with placental sharing at 12, 16, 20 and 28 weeks' gestation. On multivariate analysis, intertwin differences in fetal biometry, cord insertions and all three UV variables remained associated significantly with placental sharing at 12 and 16 weeks. However, at 20 and 28 weeks, only the intertwin EFW ratio was associated consistently with placental sharing. Fetal demise of one or both twins complicated 26 (13.0%) pregnancies. Differences in EFW and cord insertion sites were not associated significantly with fetal demise, while at 16 weeks, differences in intra-abdominal UV diameter and flow were associated with an increased risk of subsequent fetal demise. At 12 and 16 weeks' gestation, intertwin differences in UV diameter and flow reflect placental sharing more accurately than do differences in fetal growth and cord insertion sites. At 16 weeks, discordance in intra-abdominal UV diameter and flow is also associated with an increased risk of fetal demise. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Hypothesized pathogenesis of acardius acephalus, acormus, amorphus, anceps, acardiac edema, single umbilical artery, and pump twin risk prediction.

BackgroundAcardiac twinning complicates monochorionic twin pregnancies in ≈2.6%, in which arterioarterial (AA) and venovenous placental anastomoses cause a reverse circulation between prepump and preacardiac embryos and cessation of cardiac function in the preacardiac. Literature suggested four acardiac body morphologies in which select (groups of) organs fail to develop, deteriorate, or become abnormal: acephalus (≈64%, [almost] no head, part of body, legs), amorphus (≈22%, amorphous tissue lump), anceps (≈10%, cranial bones, well‐developed), and acormus (≈4%, head only). We sought to develop hypotheses that could explain acardiac pathogenesis, its progression, and develop methods for clinical testing.MethodsWe used qualitatively described pathophysiology during development, including twin‐specific AA and Hyrtl's anastomoses, the short umbilical cord syndrome, high capillary permeability, properties of spontaneous aborted embryos, and Pump/Acardiac umbilical venous diameter (UVD) ratios.ResultsWe propose that each body morphology has a specific pathophysiologic pathway. An acephalus acardius may be larger than an anceps, verifiable from UVD ratio measurements. A single umbilical artery develops when one artery, unconnected to the AA, vanishes due to flow reduction by Hyrtl's anastomotic resistance. Acardiac edema may result from acardiac body hypoxemia combined with physiological high fetal capillary permeability, high interstitial compliance and low albumin synthesis. Morphological changes may occur after acardiac onset. Pump twin risk follows from UVD ratios.ConclusionOur suggested outcomes agree reasonably well with reported onset, incidence, and progression of acardiac morphologies. Guidance for clinical prediction and testing requires ultrasound anatomy/circulation study, from the first trimester onward.

Acardiac twin pregnancies part IV: Acardiac onset from unequal embryonic splitting simulated by a fetoplacental resistance model.

Benirschke postulated that acardiac twinning occurs when markedly unequal embryonic splitting combines with arterioarterial (AA) and venovenous placental anastomoses. We tested this hypothesis by model simulations and by comparison of outcomes with 18 "pseudo-" (twin fetus with beating heart but otherwise with clear signs of an acardiac) and 3 "normal" acardiac cases. The smaller/larger cell volume ratio at embryonic splitting becomes the smaller/larger embryonic/fetal blood volume ratio (a). From a, we derived nonpulsating blood pressures using normal values (larger twin) and normal values at an appropriate earlier gestational age (smaller twin). These unequal pressure sources were used in a linear resistance fetoplacental network to calculate umbilical venous diameter ratios. Acardiac onset occurs when the smaller twin has 50% left of its normal, singleton placenta. Comparison with clinical cases approximated a by crown-rump-length-ratio to the 3rd power. Input parameters are a and the AA-radius at 40 weeks. Acardiacs can be small or large, can occur early or late, earlier at smaller a and larger AA, with larger umbilical venous diameter ratios at smaller a and smaller AA. Comparison with the 21 clinical cases was good, except for 2. Our analysis supports Benirschke's hypothesis. The smaller twin has to share its placental perfusion with the larger twin, which is a novel finding. The AA size is essential for the future of both fetuses but complicates easy understanding of (pseudo-)acardiac clinical presentations. Late acardiac onset occurs infrequently. Using nonpulsating circulations may have caused our extensive predictions of late onset. An improved model requires including hypoxemia in the smaller twin from chronic placental hypoperfusion. Birth Defects Research 109:211-223, 2017. © 2016 Wiley Periodicals, Inc.

Acardiac twin pregnancies part III: Model simulations.

Acardiac monochorionic twins lack cardiac function but grow by passive perfusion of the pump twin's deoxygenated arterial blood through placental arterioarterial (AA) and venovenous (VV) anastomoses and by hypoxia-mediated neovascularization. Pump twins therefore must continuously increase their cardiac output which may cause heart failure. Our aims were: to adapt our twin-twin transfusion syndrome model for acardiac twin pregnancies, to simulate pump and acardiac twin development, and to examine the model for early prognostic markers of pump twin survival. We used an infinite acardiac placental resistance, based on placental dye injection studies and simulations, suggesting the AA-Acardiac-VV series resistance determines the pump twin's excess cardiac output. Pump and acardiac development were expressed by the pump's excess cardiac output versus its normal value, represented by pump/acardiac umbilical venous diameter (UVD) ratios. UVD ratios distinguish between AA-VV anastomoses that do and do not cause hydropic pump twins. Pump twins can handle relative larger acardiac perfusion at later than earlier gestation. Both VV and acardiac resistances are significantly smaller than the AA resistance, based on respectively clinical data and acardiac blood volumetric growth. Our simulations support clinical results which show that UVD ratios aid in the prediction of pump twin risk. The AA anastomosis controls the future of both the pump and the acardiac. Correlation between acardiac size and pump twin risk is secondary to the AA size but remains clinically usable. These factors may aid in the development of methods for pump twin prognosis and the promotion of selective clinical interventions.Birth Defects Research (Part A), 2016.© 2016 Wiley Periodicals, Inc. Birth Defects Research (Part A) 106:1008-1015, 2016. © 2016 Wiley Periodicals, Inc.

The umbilical vein in the human fetus has a non-linear growth pattern across gestation.

Estimation of the umbilical venous blood flow volume relies on the diameter of the vein, which has been reported to be reduced in severely growth restricted fetuses. However, there is only limited information on the growth pattern of this vessel in the normal human fetus. The aim of this study is to examine the growth pattern of the umbilical vein across gestation in low-risk human pregnancies. In a prospective, longitudinal ultrasound study of 136 low-risk pregnancies, the internal diameter of the intra-amniotic portion of the umbilical vein was measured at 18, 26 and 34 weeks of gestation. To investigate the growth pattern of the venous diameter, the ratios of diameters at 26 weeks to diameters at 18 weeks (ratio 1) and the ratios at 34 to 26 weeks (ratio 2) were also calculated. A paired-sample t-test was performed to compare the means of the two ratios. The mean diameter of the umbilical vein at 18 weeks was 2.8 mm (SD 0.40), 5.8 mm (SD 0.67) at 26 weeks and 7.6 mm (SD 0.98) at 34 weeks. The mean of ratio 1 was 2.06 (95% CI 2.01-2.14), which was significantly higher than ratio 2 (mean 1.33, 95% CI 1.29-1.36), P < 0.001. The umbilical venous diameter demonstrates a non-linear growth pattern between 18 and 34 weeks of gestation. The diameter doubled in size between 18 and 26 weeks but grew at a slower rate between 26 and 34 weeks of gestation. This study provides new data on the normal growth pattern of the umbilical vein by identifying a period of gestation where its growth is accelerated.

Hypothesis acardiac twin pregnancies: Pathophysiology‐based hypotheses suggest risk prediction by pump/acardiac umbilical venous diameter ratios

A total of 75% of monozygotic twins share 1 monochorionic placenta where placental anastomoses cause several serious complications, for example, acardiac twinning. Acardiac twins lack cardiac function but grow by perfusion of arterial blood from the pump twin. This rare pregnancy has 50% natural pump twin mortality but accurate risk prediction is currently impossible. Recent guidelines suggest prophylactic surgery before 18 weeks, suggesting 50% unnecessary interventions. We hypothesize that (1) adverse pump twin outcome relates to easy-to-measure pump/acardiac umbilical venous diameter (UVD) ratios, representing acardiac perfusion by the pump's excess cardiac output. This hypothesis suggests that (2) UVD-ratios are large, mildly varying in cases without complications but small and decreasing when complications develop, thus predicting that (3) UVD-ratios may allow risk prediction of pump twins. In this exploratory clinical pilot, we tested whether UVD-ratio measurements support these predictions. We included 7 uncomplicated (expectant management), 3 elective surgical, and 17 complicated cases (pump decompensation, emergency intervention/delivery or demise). Nine UVD-ratios were measured sonographycally and 18 by pathology. Uncomplicated cases have larger, two serial measurements showing mildly varying UVD-ratios; elective surgical cases show larger UVD-ratios; complicated cases have smaller, two serial measurements showing decreasing UVD-ratios. There were no false-positives, no false-negatives and noncrossing linear trendlines of uncomplicated and complicated cohorts. Our data provide first evidence that UVD-ratios allow risk prediction of pump twins. More early uncomplicated and late complicated cases are needed, for example, in a prospective trial, before the separation between uncomplicated and complicated cohorts is accurate enough to support a well-founded decision on (early) intervention.

Ultrasound Assessment of Umbilical Cord Morphology in the First Trimester: A Feasibility Study

Objective: The aim of this study was to determine whether morphology and measurement of the umbilical cord could be accurately assessed at the time of the 11- to 13⁺⁶-week scan. Methods: We conducted a prospective study of 100 consecutive women with singleton pregnancies at 11-13⁺⁶ weeks' gestation who were seen for routine aneuploidy screening. Transabdominal ultrasound scans were performed, and the distance between two adjacent coils of the umbilical artery was measured in a free loop of umbilical cord. The antenatal umbilical coiling index (aUCI) was calculated as the inverse of this measurement (aUCI = 1/intercoil distance in cm). The maximum diameter of the umbilical vein was measured. Umbilical venous blood flow velocity was obtained using standard Doppler technique. Interobserver variability was assessed. A subjective assessment of the cord was performed using the Sepulveda system of classification to compare the reproducibility of the observations between two observers. Results: The intended measurements could be obtained in all cases. The aUCI was found to decrease with advancing gestation, while the umbilical venous diameter increased with gestation. The umbilical venous blood flow velocity also increased with gestation. Interobserver consistency in the objective measurement of the aUCI was poor (kappa 0.146). However, the Sepulveda classification system was found to be applicable and reproducible at this period of gestation (kappa 0.601). Conclusions: Umbilical cord morphology can be consistently studied in the first trimester. A subjective method of evaluation of the morphology may be a more reproducible technique until measurement strategies are refined and operator experience developed.

P05.04: Ultrasound assessment of umbilical cord morphology in the first trimester: a feasibility study

Objective: The aim of this study was to determine whether morphology and measurement of the umbilical cord could be accurately assessed at the time of the 11- to 13 +6 -week scan. Methods: We conducted a prospective study of 100 consecutive women with singleton pregnancies at 11–13 +6 weeks’ gestation who were seen for routine aneuploidy screening. Transabdominal ultrasound scans were performed, and the distance between two adjacent coils of the umbilical artery was measured in a free loop of umbilical cord. The antenatal umbilical coiling index (aUCI) was calculated as the inverse of this measurement (aUCI = 1/intercoil distance in cm). The maximum diameter of the umbilical vein was measured. Umbilical venous blood flow velocity was obtained using standard Doppler technique. Interobserver variability was assessed. A subjective assessment of the cord was performed using the Sepulveda system of classification to compare the reproducibility of the observations between two observers. Results: The intended measurements could be obtained in all cases. The aUCI was found to decrease with advancing gestation, while the umbilical venous diameter increased with gestation. The umbilical venous blood flow

Endothelial NO Synthase Augments Fetoplacental Blood Flow, Placental Vascularization, and Fetal Growth in Mice

It is not known whether eNOS deficiency in the mother or the conceptus (ie, placenta and fetus) causes fetal growth restriction in mice lacking the endothelial NO synthase gene (eNOS knockout [KO]). We hypothesized that eNOS sustains fetal growth by maintaining low fetoplacental vascular tone and promoting fetoplacental vascularity and that this is a conceptus effect and is independent of maternal genotype. We found that eNOS deficiency blunted fetal growth, and blunted the normal increase in umbilical blood flow and umbilical venous diameter and the decrease in umbilical arterial Resistance Index in late gestation (14.5-17.5 days) in eNOS KO relative to C57Bl/6J controls. On day 17.5, fetoplacental capillary lobule length and capillary density in vascular corrosion casts were reduced in eNOS KO placentas. Reduced vascularization may be a result of decreased vascular endothelial growth factor mRNA and protein expression in eNOS KO placentas at this stage. These factors, combined with significant anemia found in eNOS KO fetuses, would be anticipated to reduce fetal oxygen delivery and contribute to the fetal tissue hypoxia that was detected in the heart, lung, kidney, and liver by immunohistochemistry using pimonidazole. Although maternal eNOS deficiency impairs uteroplacental adaptations to pregnancy, maternal genotype was not a significant factor affecting growth in heterozygous conceptuses. This indicates that fetal growth restriction was primarily caused by conceptus eNOS deficiency. In mice, placental hemodynamic and vascular changes with gestation and growth restriction showed strong parallels with human pregnancy. Thus, the eNOS KO model could provide insights into the pathogenesis of human intrauterine growth restriction.

Relationship of umbilical vein blood flow to growth parameters in the human fetus

Objective: Our purposes were to determine the relationship of the growth of umbilical blood flow to growth in body measurements of human fetuses in uncomplicated pregnancies. The study also aimed to assess the relative contributions of growth in umbilical vein diameter and of increased velocity to the increase in umbilical blood flow. Study Design: An animal study was conducted to assess the accuracy of umbilical vein blood flow measurements obtained by triplex mode ultrasonography. Seven pregnant ewes underwent triplex mode umbilical vein flow determination. These results were compared with historical flow data obtained by a steady-state diffusion technique in 34 ewes matched for gestational age and weight. In a separate study performed on human beings, reproducibility and precision of triplex mode flow determination were assessed, as were the relationships between umbilical vein flow and gestational age and head and abdominal circumferences. This cross-sectional study was performed with 70 healthy fetuses ranging from 20 weeks’ gestation to term. Best-fit interpolating equations and confidence limits were calculated for blood flow measurements versus gestational age and head and abdominal circumferences. Results: In the validation study performed on sheep there were no significant differences between triplex mode and steady-state measurement groups with respect to gestational age or weight. The umbilical vein flows were similar between triplex mode and steady-state measurement groups ( P = .881). In the human study the intraobserver and interobserver coefficients of variation for the vein diameter, mean velocity, and absolute umbilical vein blood flow varied from 2.9% to 12.7%. The mean duration of examination was 3 ± 1 minutes. The umbilical vein diameter and mean velocity increased throughout pregnancy. The absolute umbilical vein flow increased exponentially from 97.3 mL/min at midgestation to 529.1 mL/min at 38 weeks’ gestation, whereas umbilical vein flow per kilogram of fetal weight did not change significantly with gestational age. There was a strong correlation between absolute umbilical vein flow and the fetal head and abdominal circumferences. Conclusions: The triplex mode ultrasonographic technique can play an innovative role in obtaining quick and reproducible measurements of umbilical vein blood flow. The approach was validated with a sheep model. Umbilical vein blood normalized for fetal weight (milliliters per minute per kilogram of fetal weight) and absolute flow (in milliliters per minute) are consistent with previous human studies. We have established new reference values of umbilical vein blood flow relative to head and abdominal circumferences. The growth of umbilical venous diameter accounted for most of the growth in umbilical vein flow. (Am J Obstet Gynecol 1999;181:174-9.)

Evaluation of umbilical venous blood flow by Doppler color flow mapping and conventional ultrasonographic methods.

Ultrasonographic measurement of umbilical venous blood flow as a reflection of placental blood flow has been used for assessment of fetal well-being. Because fetal and maternal factors may prevent satisfactory measurement of umbilical venous diameter and flow velocity, an alternative method would be helpful. We found that, in 35 human fetuses between 18 and 35 weeks of gestation, that both variables for umbilical venous flow calculation can be measured from a single Doppler color frame with close measurement agreement to conventional combined cross-sectional pulsed Doppler ultrasonographic measurements. Thus, this method provides an alternative to the conventional method or may be used for a cross-check and has the potential for automated flow calculation.