Umbilical venous volume flow and fetal behavioral states in the normally developing fetus

Value of foetal umbilical vein standardised blood flow volume in predicting weight gain in the third trimester: a prospective case-cohort study

Objective

This study aims to establish a prediction model of foetal umbilical vein standardised blood flow volume (sQuv) on estimated foetal weight (EFW) in the third trimester.

Methods

A case-cohort study involving 200 eligible normal foetuses was conducted at the Ultrasound Department of Longquanyi District of Maternity and Child Healthcare Hospital between June 1, 2020 and December 31, 2021. Ultrasound measurements were taken at two separate intervals to assess EFW and the rate of EFW (rEFW) [first: between 28 w and 33 w6d of gestational age (GA); second: after 4-6 weeks]. Umbilical vein blood flow volume (Quv) and sQuv (normalised with EFW) were calculated only during the initial measurement. Using general linear regression, a prediction model for EFW based on GA and sQuv was developed, with the gestational week employed as a calibration scalar and validated using linear regression cross-validation.

Results

In the third trimester, EFW exhibited significant correlations with GA, abdominal circumference (AC), head circumference (HC) and Quv (all ρ > 0.6, P < 0.001). Furthermore, the rEFW showed significant correlations with Quv and sQuv (all ρ > 0.6, P < 0.001). A linear regression equation was established using a general linear regression model: rEFW = 0.32689 × sQuv. Additionally, a foetal weight prediction model (EFW = -2,554.6770 + 0.9655 × sQuv + 129.6916 × GA) was established using sQuv. The above two formulas were cross-validated by intra-group linear regression and proved to be of good efficacy.

Conclusions

In the third trimester, EFW displayed significant correlations with GA, AC, HC and Quv. Additionally, the rEFW exhibited significant correlations with Quv and sQuv. The sQuv during the third trimester has predictive value for foetal weight, serving as an early warning indicator.

Placental assessment using spectral analysis of the envelope of umbilical venous waveforms in sheep

INTRODUCTION

This study was designed to test the efficacy of an ultrasound flow measurement method to evaluate placental function in a hyperandrogenic sheep model that produces placental morphologic changes and an intrauterine growth restriction (IUGR) phenotype.

MATERIALS AND METHODS

Pregnant ewes were assigned randomly between control (n = 12) and testosterone-treatment (T-treated, n = 22) groups. The T-treated group was injected twice weekly intramuscularly (IM) with 100 mg testosterone propionate. Control sheep were injected with corn oil vehicle. Lambs were delivered at 119.5 ± 0.48 days gestation. At the time of delivery of each lamb, flow spectra were generated from one fetal artery and two fetal veins, and the spectral envelopes examined using fast Fourier transform analysis. Base 10 logarithms of the ratio of the amplitudes of the maternal and fetal spectral peaks (LRSP) in the venous power spectrum were compared in the T-treated and control populations. In addition, we calculated the resistive index (RI) for the artery defined as ((peak systole - min diastole)/peak systole). Two-tailed T-tests were used for comparisons.

RESULTS

LRSPs, after removal of significant outliers, were -0.158 ± 0.238 for T-treated and 0.057 ± 0.213 for control (p = 0.015) animals. RIs for the T-treated sheep fetuses were 0.506 ± 0.137 and 0.497 ± 0.086 for controls (p = 0.792) DISCUSSION: LRSP analysis distinguishes between T-treated and control sheep, whereas RIs do not. LRSP has the potential to identify compromised pregnancies.

Comparison of Variations Between Spectral Doppler and Gaussian Surface Integration Methods for Umbilical Vein Blood Volume Flow

OBJECTIVES

We are studying a new method for estimating blood volume flow that uses 3-dimensional ultrasound to measure the total integrated flux through an ultrasound-generated Gaussian surface that intersects the umbilical cord. This method makes none of the assumptions typically required with standard 1-dimensional spectral Doppler volume flow estimates. We compared the variations in volume flow estimates between techniques in the umbilical vein.

METHODS

The study was Institutional Review Board approved, and all 12 patients gave informed consent. Because we had no reference standard for the true umbilical vein volume flow, we compared the variations of the measurements for the flow measurement techniques. At least 3 separate spectral Doppler and 3 separate Gaussian surface measurements were made along the umbilical vein. Means, standard deviations, and coefficients of variation (standard deviation/mean) for the flow estimation techniques were calculated for each patient. P < .05 was considered significant.

RESULTS

The ranges of the mean volume flow estimates were 174 to 577 mL/min for the spectral Doppler method and 100 to 341 mL/min for the Gaussian surface integration (GSI) method. The mean standard deviations (mean ± SD) were 161 ± 95 and 45 ± 48 mL/min for the spectral Doppler and GSI methods, respectively (P < .003). The mean coefficients of variation were 0.46 ± 0.17 and 0.18 ± 0.14 for the spectral Doppler and GSI methods respectively (P < 0.002).

CONCLUSIONS

The new volume flow estimation method using 3-dimensional ultrasound appears to have significantly less variation in estimates than the standard 1-dimensional spectral Doppler method.

Mid-gestational fetal placental blood flow is diminished in the fetus with congenital heart disease

OBJECTIVE

Data suggest fetuses with congenital heart disease (CHD) have placental abnormalities. Their abnormal placental vasculature may affect fetal placental blood flow, which has not previously been explored.

METHOD

We performed a retrospective cross-sectional study comparing umbilical venous volume flow (UVVF) of single ventricle, D-transposition of the great arteries, and tetralogy of Fallot fetuses with fetuses without CHD. UVVF and combined cardiac output (CCO) were calculated from fetal echocardiography and compared using t tests, χ² and Fisher's exact tests.

RESULTS

Mean gestational age and fetal weight were greater in CHD fetuses (26.5 weeks, 1119.4 g; n = 81, P < .001) compared to controls (23.1 weeks, 675 g; n = 170, P < .001). UVVF/fetal weight was nevertheless decreased among cases (99.8 vs 115.3 mL/min/kg, P < .001). Subgroup analysis of 20- to 25-week fetuses demonstrated no significant differences in case and control baseline characteristics. In CHD fetuses (n = 31) compared to controls (n = 144), absolute UVVF (50.8 vs 62.1 mL/min, P = .006), and UVVF/fetal weight (98.8 vs 118.5 mL/min/kg, P < .001) were decreased. Findings were similar in single ventricle (n = 24) and hypoplastic left heart syndrome (n = 14).

CONCLUSION

Mid-gestational placental blood flow in CHD fetuses is decreased compared to controls. Further study is needed to explore the relationship between UVVF and placental pathology, and impact on outcomes.

Uterine artery and umbilical vein blood flow are unaffected by moderate habitual physical activity during pregnancy

OBJECTIVE

This study aims to noninvasively quantify blood flow in the uterine arteries (UTAs) and umbilical vein (UV) using phase-contrast magnetic resonance imaging (PC-MRI) and test whether these correlate with maternal fitness parameters.

METHOD

Resting UTA and UV flows were measured in 23 healthy 30 ± 3-year-old women who engaged in moderate-intensity physical activity during pregnancy. Participant fitness was characterized in the second and third trimesters using the submaximal oxygen uptake (VO₂ ) test measuring heart rate (HR), VO₂ , ventilation (ventilatory equivalent [VE]/VO₂ ), and the Borg rating of perceived exertion (respiratory quotient [RQ]). Linear regression models were used to determine the associations between blood flow and maternal fitness measures.

RESULTS

Blood flows in the UTA (957 ± 241 mL/min) and UV (132 ± 38 mL/min/kg) were successfully measured in 20 (87%) participants. Neither was associated with any physical fitness parameters (HR, VO₂ , VE/VO₂ , and RQ) nor with any second-to-third trimester change in these parameters.

CONCLUSION

PC-MRI can be used to noninvasively measure blood flow in the UTA and UV. Neither resting UTA nor UV flow is associated with maternal fitness parameters. This is the first MRI-based study to provide novel hemodynamic data suggesting decoupling between maternal moderate fitness level and the maternal-placental-fetal hemodynamic system in healthy, normal body mass index (BMI) pregnancies.

Placenta-on-a-Chip: In Vitro Study of Caffeine Transport across Placental Barrier Using Liquid Chromatography Mass Spectrometry

Due to the particular structure and functionality of the placenta, most current human placenta drug testing methods are limited to animal models, conventional cell testing, and cohort/controlled testing. Previous studies have produced inconsistent results due to physiological differences between humans and animals and limited availability of human and/or animal models for controlled testing. To overcome these challenges, a placenta-on-a-chip system is developed for studying the exchange of substances to and from the placenta. Caffeine transport across the placental barrier is studied because caffeine is a xenobiotic widely consumed on a daily basis. Since a fetus does not carry the enzymes that inactivate caffeine, when it crosses a placental barrier, high caffeine intake may harm the fetus, so it is important to quantify the rate of caffeine transport across the placenta. In this study, a caffeine concentration of 0.25 mg mL-1 is introduced into the maternal channel, and the resulting changes are observed over a span of 7.5 h. A steady caffeine concentration of 0.1513 mg mL-1 is reached on the maternal side after 6.5 h, and a 0.0033 mg mL-1 concentration on the fetal side is achieved after 5 h.

Unexpected middle cerebral artery peak systolic velocity values in the normal fetal population. Are they a matter of concern?

Objective: The aim of this study was to investigate in the fetus the relationship between unexpected high middle cerebral artery peak systolic velocity (middle cerebral artery (MCA) peak systolic velocity (PSV)) values and hemoglobin (Hgb) levels in normal pregnancies without conditions leading to fetal anemia.Material and methods: This was a prospective study of 922 singleton low-risk pregnant women attending the maternity of La Fe Hospital between 35 and 41 weeks. Multiple pregnancies and pregnancies with growth restriction, smallness, macrosomia or conditions leading to fetal anemia were excluded. During each examination, a biometry and a Doppler examination of the umbilical artery pulsatility index (umbilical artery (UA) pulsatility index (PI)), MCA PI and MCA PSV were performed. MCA PSV was converted into multiples of median (MoM), and birth weight (BW) into centiles adjusting for gender. All pregnancies delivered in a 2-week interval since examination. In order to explain Hgb levels at birth, a correlation between MCA PSV MoM and Hgb was performed and Hgb levels of fetuses with normal MCA PSV and abnormal MCA PSV were compared, using 1.3 MoM as cut-off for mild anemia. Finally, a multivariate linear regression analysis was performed including MCA PSV MoM and several Doppler and clinical parameters.Results: The univariate analysis showed no correlation between the MCA PSV MoM and the umbilical artery Hgb (r² = 0.026, p = .1237) while a weak correlation was found with the umbilical vein Hgb (r² = 0.0053, p = .027). Also, fetuses with values of MCA PSV MoM <1.3 MoM did not differ in terms of artery and vein Hgb with those presenting values >1.3 MoM (p = .99 and p = .61, respectively). Finally, both prediction models explaining arterial and venous Hgb presented very weak predictive accuracies (R Squared: 0.0965 and R Squared: 0.106) indicating a low possibility to diagnose fetal anemia in otherwise normal fetuses based on clinical and sonographic data.Conclusion: In normal pregnancies that are not suffering from conditions leading to fetal anemia, unexpected high MCA PSV values do not necessarily reflect the presence of this condition. Active management in this circumstance might result in unjustified higher rates of labor induction and operative delivery.

Evaluation of Umbilical Vein Blood Volume Flow in Preeclampsia by Angle-Independent 3D Sonography

OBJECTIVES

To investigate the association between umbilical vein blood volume flow and the condition of preeclampsia in an at-risk maternal patient cohort. Umbilical vein volume flow was quantified by a 3-dimensional (3D) sonographic technique that overcomes several limitations of standard sonographic flow measurement methods.

METHODS

A total of 35 patients, each with a singleton pregnancy, were recruited to provide 5 patients with preeclampsia, derived as a subset from a 26-patient at-risk group, and 9 patients with normal pregnancies. An ultrasound system equipped with a 2.0-8.0-MHz transducer was used to acquire multivolume 3D color flow and power mode data sets to compute the mean umbilical vein volume flow in patients with normal pregnancies and preeclampsia.

RESULTS

The gestational ages of the pregnancies ranged from 29.7 to 34.3 weeks in the patients with preeclampsia and from 25.9 to 34.7 weeks in the patients with normal pregnancies. Comparisons between patients with normal pregnancies and those with preeclampsia showed weight-normalized flow with a moderately high separation between groups (P = .11) and depth-corrected, weight-normalized flow with a statistically significant difference between groups (P = .035). Umbilical vein volume flow measurements were highly reproducible in the mean estimate, with an intrapatient relative SE of 12.1% ± 5.9% and an intrameasurement relative SE of 5.6% ± 1.9 %. In patients who developed pregnancy-induced hypertension or severe pregnancy-induced hypertension, umbilical vein volume flow suggested gestational hypertensive disorder before clinical diagnosis.

CONCLUSIONS

Results indicate that mean depth-corrected, weight-normalized umbilical vein volume flow is reduced in pregnancies complicated by preeclampsia and that volume flow may indicate hypertensive disorder earlier in gestation. Volume flow measurements are highly reproducible, and further study in a larger clinical population is encouraged to determine whether 3D volume flow can complement the management of preeclampsia and, in general, at-risk pregnancy.

Foetal volumetry using magnetic resonance imaging in intrauterine growth restriction

OBJECTIVES

We used magnetic resonance imaging (MRI) to perform volumetry of foetuses with and without growth restriction, and identify deviations in organ growth.

STUDY DESIGN

20 growth restricted and 19 normal foetuses were scanned once during pregnancy at gestational age 20.53-36.57 weeks. MRI scans were performed on a 1.5T system using ssFSE sequences. Manual segmentation of whole body, brain, heart, lung, liver, thymus and kidney volume was performed. Data on the severity of foetal growth restriction and pregnancy outcome was collected.

RESULTS

There was a significant reduction in foetal whole body volume and volume of all internal organs except the brain in growth restricted foetuses. A brain:liver ratio above 3.0 was associated with a 3.3 fold increase in risk of perinatal mortality (95% CI=1.68-6.47).

CONCLUSION

MRI provides an accurate assessment of foetal organ growth. It may have a role to play in monitoring disease severity and the effect of future interventions.

Regulation of transplacental water transfer: the role of fetoplacental venous tone

We used the in vitro dually perfused human placental lobule to test the hypothesis that known vasoconstrictors of the fetal placental circulation, angiotensin II and the thromboxane mimetic U46619 could induce fetomaternal water transfer. Secondly, we used a combination of vasoconstrictor and mechanically induced increases in fetal placental circulatory pressure to examine the role of the venous system in this context. Fetal-side administration of angiotensin II (A-II) and U46619 (n=6 and n=9, for A-II and U46619, respectively) induced dose dependent, recoverable elevations in fetal inflow hydrostatic pressure (HP; A-II: maximum contractility=83 mmHg, EC50=22.0 nM; U46619: maximum contractility was not achieved, but exceeded the A-II effect) and loss of perfusate from the fetal side (A-II: EC50=70.2 nM, maximum fetal-side solvent loss=1906 microl/min; U46619: maximum fetal-side solvent loss was not achieved, but exceeded the A-II effect). Fetal-side solvent loss, for both agonists, was correlated linearly with fetomaternal inflow HP (FMIHP) in a biphasic manner (between 0 and 30 mmHg the slopes (+/-S.E.) were 6.4+/-2.2 and 17.1+/-5.8 microl/(min mmHg) for A-II and U46619, respectively; between 30 and 70 mmHg the slopes (+/-S.E.) were 35.6+/-6.5 and 43.7+/-15.9 microl/(min mmHg) for A-II and U46619, respectively). Increasing fetal-side lumenal pressure (n=3) by raising the fetal outflow catheter caused a loss of perfusate from the fetal side which was reduced in the presence of U46619 (fetal solvent loss per unit increase in fetal-side inflow HP: slopes were 1.198+/-0.123 and 0.783+/-0.085 microl/(min mmHg mmHg), respectively). Notwithstanding the possibility of fetoplacental arterial constriction, we conclude that vasoconstrictive agonists in the fetoplacental circulation affect venous resistance, causing fetomaternal fluid loss. These observations could be relevant to the oligohydramnios associated with intrauterine growth restriction, a condition associated with increased resistance in the umbilical circulation.