Fetal umbilical artery flow velocity waveforms and placental resistance: clinical significance

A longitudinal and cross-sectional study of placental circulation between normal and placental insufficiency pregnancies

INTRODUCTION

To longitudinally and cross-sectionally study the differences in the uterine artery pulsatility index (UTPI), umbilical artery pulsatility index (UAPI) and placental vascularization indices (PVIs, derived from 3-dimensional power Doppler) between normal and placental insufficiency pregnancies throughout gestation.

METHODS

UTPI, UAPI and PVI were measured 6 times at 4- to 5- week intervals from 11 to 13+6 weeks-36 weeks. Preeclampsia (PE) and fetal growth restriction (FGR) were defined as placental insufficiency. Comparisons of UTPI, UAPI and PVI between normal and insufficiency groups were performed by one-way repeated measures analysis of variance.

RESULTS

A total of 125 women were included: monitored regularly from the first trimester to 36 weeks of gestation: 109 with normal pregnancies and 16 with placental insufficiency. Longitudinal study of the normal pregnancy group showed that UTPI and UAPI decreased significantly every 4 weeks, while PVIs increased significantly every 8 weeks until term. In the placental insufficiency group however, this decrease occurred slower at 8 weeks intervals and UTPI stabilized after 24 weeks. No significant difference was noted in PVIs throughout pregnancy. Cross-sectional study from different stages of gestation showed that UTPI was higher in the insufficiency group from 15 weeks onward and PVIs were lower after 32 weeks.

DISCUSSION

Compared to high-risk pregnancies with normal outcome, UTPI and UAPI needed a longer time to reach a significant change in those with clinical confirmation of placental insufficiency pregnancies and no significant change was found in PVI throughout gestation. UTPI was the earliest factor in detecting adverse outcome pregnancies.

Hemodynamic changes and perinatal outcome associated with umbilical artery thrombosis: a retrospective study

OBJECTIVE

Poor fetal and perinatal outcomes in fetuses associated with umbilical artery thrombosis (UAT), such as severe intrauterine growth restriction (IUGR) and intrauterine asphyxia have been reported by some case series. Its hemodynamic impact remains unclear. The aim of this study was to evaluate the hemodynamic changes and perinatal outcome in UAT fetuses with a relatively large sample.

METHODS

We included singleton fetuses diagnosed with UAT and with at least one available Doppler evaluation before the end of pregnancy in our center from 2016 to 2023. Fetuses with structural abnormalities and with no follow-up results were excluded. Doppler waveforms from the Umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV) and uterine artery (UtA) were routinely evaluated according to ISUOG Practice Guidelines from diagnosis. The same sample of GA-matched normal fetuses with Doppler measurements during the same period were randomly selected as control group.

RESULTS

Eighty-nine singleton fetuses with UAT with at least one Doppler evaluation before the end of pregnancy were identified, 13 fetuses with no follow-up results were excluded. After comprehensive prenatal counseling, 14 cases received urgent cesarean section, the remaining 55 cases received expectant management, the median day between GA at diagnosis and end of pregnancy was 13 (5-53) days (range, 2-159). 7 (7/76, 9.2%) cases occurred stillbirth, and the incidence of IUGR and Neonatal Intensive Care Unit (NICU) admission were 18.4% (14/76) and 13.2% (10/76) respectively. 49 fetuses (49/76, 64.5%) combined with Doppler abnormalities. UA abnormalities (35/76, 46.1%) and MCA abnormalities (34/76, 44.7%) were the most changes at presentation. Compared to control group, UA-EDV was significantly increased in UAT fetuses [21.84 (15.59-26.64) vs. 16.40 (12.43-20.70) cm/s, p < 0.001], UA-PI and UA-RI significantly decreased [0.68 (0.57-0.84) vs. 0.92 (0.79-1.11), p<0.001; 0.51 (0.44-0.59) vs. 0.62 (0.55-0.68), p < 0.001, respectively]. Both the MCA-PSV and MCA-EDV were significantly higher in UAT fetuses [54.60 (48.00-61.34) vs. 44.47 (29.66-57.60) cm/s, p < 0.001; 11.19 (7.84-17.60) vs. 8.22 (5.21-12.00) cm/s, p < 0.001, respectively], this led to a lower MCA-PI and MCA-RI. Meanwhile, DV-PIV was significantly higher in UAT fetuses [0.6 (0.47-0.87) vs. 0.45 (0.37-0.55), p < 0.001], CPR and UtA-PI were no significant difference between these two groups. Multivariate logistic regression analysis showed that DV-PIV was an independent risk factor for adverse pregnancy outcomes (OR 161.922, p<0.001), the area under the ROC curve (AUC) was 0.792 (95% CI 0.668-0.917; p < 0.001).

CONCLUSION

Our data showed serious adverse pregnancy consequences are combined with UAT fetuses. Hemodynamic changes in UAT fetuses showed the remaining artery for compensation and brain perfusion derangement. With a comprehensive and standardized Doppler evaluation, progression of fetal deterioration may be detailed presented.

Fetoplacental vascular effects of maternal adrenergic antihypertensive and cardioprotective medications in pregnancy

Maternal cardiovascular diseases, including hypertension and cardiac conditions, are associated with poor fetal outcomes. A range of adrenergic antihypertensive and cardioprotective medications are often prescribed to pregnant women to reduce major maternal complications during pregnancy. Although these treatments are not considered teratogenic, they may have detrimental effects on fetal growth and development, as they cross the fetoplacental barrier, and may contribute to placental vascular dysregulation. Medication risk assessment sheets do not include specific advice to clinicians and women regarding the safety of these therapies for use in pregnancy and the potential off-target effects of adrenergic medications on fetal growth have not been rigorously conducted. Little is known of their effects on the fetoplacental vasculature. There is also a dearth of knowledge on adrenergic receptor activation and signalling within the endothelium and vascular smooth muscle cells of the human placenta, a vital organ in the maintenance of adequate blood flow to satisfy fetal growth and development. The fetoplacental circulation, absent of sympathetic innervation, and unique in its reliance on endocrine, paracrine and autocrine influence in the regulation of vascular tone, appears vulnerable to dysregulation by adrenergic antihypertensive and cardioprotective medications compared with the adult peripheral circulation. This semi-systematic review focuses on fetoplacental vascular expression of adrenergic receptors, associated cell signalling mechanisms and predictive consequences of receptor activation/deactivation by antihypertensive and cardioprotective medications.

Imperatives of Mathematical Model of Arterial Blood Dynamics for Interpretation of Doppler Velocimetry: A Narrative Review

Clinicians frequently study arterial Doppler velocimetric waveforms depicted by Doppler sonography of the kidneys, the heart, the brain, and the feto-maternal circulation to assess the well-being of the aforementioned vital organs. The waveform interpretation of the Doppler indices can be studied using a mathematical model. The developed models serve as teaching tools and for easy comprehension of the regulatory mechanism of the organs. It will also obtain accurate wall shear stress (WSS) and likely atherosclerotic sites can be predicted early. The aim of this review is to reveal the imperatives of mathematical models in the study of the physical interpretation of Doppler velocimetry. The models will explore sonographic Doppler velocimetry and computational fluid dynamics (CFD) in determining the segments of the arteries that are prone to the development of atheromatous plaque. It will be achieved by comparing and computing the measurement differences of the WSS. A thorough literature review was carried out between 1971 and 2021 on the mathematical modeling of blood dynamics and Doppler velocimetry of different blood vessels, across various electronic databases including NC AHEC Digital Library, PUBMED, ERIC, MEDLINE, Free Medical Journals, and EMBASE. The results of the literature search were presented using the PRISMA flow chat. The narrative review of the mathematical models of arterial blood dynamics is based on incompressible Navier-Stokes equations, the Windkessel model, and CFD. It was deduced that the blood flow velocity decreased with time across the varying frequency from 0.2Hz to 0.50Hz in the interlobar arterial channels. The review also revealed that adult humans' Doppler indices of the renal-interlobar artery agree with developed models of renal interlobar arterial blood dynamics. The mathematical model measurements of the great vessels matched the sonographic Doppler velocimetry with <15% variation. In our fast-paced world of epidemiological transition, the imperatives of mathematical modeling of arterial flow dynamics based on the Navier-Stokes equations to represent various physiologic and pathologic situations cannot be overstated. The practical consequences include the possibility of mathematical models to acquire precise WSS distribution and early detection of potential atherosclerotic sites during cardiovascular Doppler sonography.

Impact on postoperative, neonatal and 2-year neurodevelopmental outcomes of UA-AREDF during and after fetal spina bifida repair

OBJECTIVE

Absent or reversed end-diastolic flow (AREDF) in the umbilical artery (UA) on Doppler is a known phenomenon during fetal interventions, such as fetal open spina bifida (OSB) repair. We aimed to evaluate the clinical importance of these Doppler findings by investigating the impact of UA-AREDF on postoperative, neonatal and 2-year neurodevelopmental outcomes.

METHODS

This was a prospective study of pregnancies undergoing fetal OSB repair at the Zurich Center for Fetal Diagnosis and Therapy between 2010 and 2019. The group with UA-AREDF during or immediately after the intervention was compared to the group with normal UA Doppler. Primary endpoint was the FIGO scores of cardiotocography (CTG) 1, 2 and 6 h postoperatively and on day 1 after surgery. Secondary endpoints were the neonatal parameters and 2-year neurodevelopmental outcome assessed using the Bayley Scales of Infant and Toddler Development, Third Edition.

RESULTS

Data of 130 patients were analyzed. None of the fetuses had UA-AREDF before OSB repair. Normal UA Doppler was observed in 107 (82%) patients and UA-AREDF was observed in 23 (18%) during or immediately after OSB surgery. UA-AREDF was more often observed after version of the fetus (P = 0.045). Seventeen (13%) cases had absent end-diastolic flow (UA-AEDF) and six (5%) cases had reversed end-diastolic flow (UA-REDF). UA-AREDF disappeared in all 23 cases within the first day after OSB surgery. One-third of all CTGs were restricted in oscillation after surgery, but no significant difference in CTG 1, 2 and 6 h postoperatively or on the first postoperative day was found between the UA-AREDF and normal-Doppler groups (P > 0.05). Gestational age at delivery, UA pH, 5-min Apgar score and birth weight were comparable between the two groups, and there was no difference in the 2-year neurodevelopmental outcome (P > 0.05). The neonatal and 2-year neurodevelopmental outcomes also did not differ significantly between the UA-REDF and UA-AEDF groups.

CONCLUSIONS

Postoperative CTG abnormalities occur and recover at a similar rate in fetuses with transitory UA-AREDF and those with normal Doppler during fetal OSB repair. UA-AREDF during fetal OSB repair did not negatively influence postnatal or 2-year neurodevelopmental outcomes. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Fetal Biometric Assessment and Infant Developmental Prognosis of the Tadalafil Treatment for Fetal Growth Restriction

Background and Objectives: Tadalafil is expected to treat fetal growth restriction (FGR), a risk factor for stillbirth and neonatal morbidity. This study aimed to evaluate the fetal biometric growth pattern of fetuses with FGR treated with tadalafil by ultrasonographic assessment. Materials and Methods: This was a retrospective study. Fifty fetuses diagnosed with FGR and treated by maternal administration of tadalafil and ten controls who received conventional treatment at Mie University Hospital from 2015 to 2019 were assessed. Fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) at the start of treatment and at two weeks and four weeks of treatment were mainly assessed by ultrasound examination. The Wilcoxon signed-rank test was used to assess the measures. The Kyoto Scale of Psychological Development (KSPD) was used to assess the developmental prognosis on tadalafil-treated children at 1.5 years of corrected age (CA) and 3 years old. Results: The median gestational age at the start of treatment was 30 and 31 weeks in the tadalafil and control groups, respectively, and the median gestational age at delivery was 37 weeks in both groups. The Z-score of HC was significantly increased at 4 weeks of treatment (p = 0.005), and the umbilical artery resistance index was significantly decreased (p = 0.049), while no significant difference was observed in the control group. The number of cases with an abnormal score of less than 70 on the KSPD test was 19% for P-M, 8% for C-A, 19% for L-S, and 11% for total area at 1.5 years CA. At 3 years old, the respective scores were 16%, 21%, 16%, and 16%. Conclusions: Tadalafil treatment for FGR may maintain fetal HC growth and infants' neuro-developmental prognosis.

The Effect of External Cephalic Version on Fetal Circulation: A Prospective Cohort Study

External cephalic version (ECV) is a cost-effective and safe treatment option for breech presentation at term. Following ECV, fetal well-being is assessed via a non-stress test (NST). An alternative option to identify signs of fetal compromise is via the Doppler indices of the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV). Inclusion criteria were an uncomplicated pregnancy with breech presentation at term. Doppler velocimetry of the UA, MCA and DV were performed up to 1 h before and up to 2 h after ECV. The study included 56 patients who underwent elective ECV with a success rate of 75%. After ECV, the UA S/D ratio, UA pulsatility index (PI) and UA resistance index (RI) were increased compared to before the ECV (p = 0.021, p = 0.042, and p = 0.022, respectively). There were no differences in the Doppler MCA and DV before or after ECV. All patients were discharged after the procedure. ECV is associated with changes in the UA Doppler indices that might reflect interference in placental perfusion. These changes are probably short-term and have no detrimental effects on the outcomes of uncomplicated pregnancies. ECV is safe; yet it is a stimulus or stress that can affect placental circulation. Therefore, careful case selection for ECV is important.

Changes in Artery Diameters and Fetal Growth in Cases of Isolated Single Umbilical Artery

Background-There are conflicting data in the international literature on the risks of abnormal fetal growth in fetuses presenting an isolated single umbilical artery (SUA), and the pathophysiology of this complication is poorly understood. Objective-To evaluate if changes in diameter of the remaining umbilical artery in fetuses presenting an isolated SUA are associated with different fetal growth patterns. Study design-This was a two-center prospective longitudinal observational study including 164 fetuses diagnosed with a SUA at the 20-22-week detailed ultrasound examination and 200 control fetuses with a three-vessel cord. In all cases, the diameters of the cord vessels were measured in a transverse view of the central portion of the umbilical cord, and the number of cord vessels was confirmed at delivery. Logistic regression and nonparametric receiver operating characteristic (ROC) analysis were carried out to evaluate the association of the umbilical artery diameter in a single artery with small for-gestational age (SGA) and with fetal growth restriction (FGR). The impact of artery dimension was adjusted for maternal BMI, parity, ethnicity, side of the remaining umbilical artery and umbilical resistance index (RI) in the regression model. Results-A significantly (p < 0.001) larger mean diameter was found for the remaining artery in fetuses with SUA compared with controls (3.0 ± 0.9 vs. 2.5 ± 0.6 mm). After controlling for BMI and parity, we found no difference in umbilical resistance and side of the remaining umbilical artery between the SUA and control groups. A remaining umbilical artery diameter of >3.1 mm was found to be associated with a lower risk of FGR, but this association failed to be statistical significant (OR = 0.60, 95% CI = 0.33-1.09, p value = 0.089). We also found that the mean vein-to-artery area ratio was significantly (p < 0.001) increased in the SUA group as compared with the controls (2.4 ± 1.8 vs. 1.8 ± 0.9; mean difference = 0.6; Cohen's d = 0.46). Conclusion-In most fetuses with isolate SUA, the remaining artery diameter at 20-22 weeks is significantly larger than in controls. When there are no changes in the diameter and, in particular, if it remains <3.1 mm, the risk of abnormal fetal growth is higher, and measurements of the diameter of the remaining artery could be used to identify fetuses at risk of FGR later in pregnancy.

Altered Cord Blood Lipid Concentrations Correlate with Birth Weight and Doppler Velocimetry of Fetal Vessels in Human Fetal Growth Restriction Pregnancies

Fetal growth restriction (FGR) is associated with short- and long-term morbidity, often with fetal compromise in utero, evidenced by abnormal Doppler velocimetry of fetal vessels. Lipids are vital for growth and development, but metabolism in FGR pregnancy, where fetuses do not grow to full genetic potential, is poorly understood. We hypothesize that triglyceride concentrations are increased in placentas and that important complex lipids are reduced in cord plasma from pregnancies producing the smallest babies (birth weight &lt; 5%) and correlate with ultrasound Dopplers. Dopplers (umbilical artery, UA; middle cerebral artery, MCA) were assessed longitudinally in pregnancies diagnosed with estimated fetal weight (EFW) &lt; 10% at ≥29 weeks gestation. For a subset of enrolled women, placentas and cord blood were collected at delivery, fatty acids were extracted and targeted lipid class analysis (triglyceride, TG; phosphatidylcholine, PC; lysophosphatidylcholine, LPC; eicosanoid) performed by LCMS. For this sub-analysis, participants were categorized as FGR (Fenton birth weight, BW ≤ 5%) or SGA "controls" (Fenton BW &gt; 5%). FGRs (n = 8) delivered 1 week earlier (p = 0.04), were 29% smaller (p = 0.002), and had 133% higher UA pulsatility index (PI, p = 0.02) than SGAs (n = 12). FGR plasma TG, free arachidonic acid (AA), and several eicosanoids were increased (p &lt; 0.05); docosahexaenoic acid (DHA)-LPC was decreased (p &lt; 0.01). Plasma TG correlated inversely with BW (p &lt; 0.05). Plasma EET, non-esterified AA, and DHA correlated inversely with BW and directly with UA PI (p &lt; 0.05). Placental DHA-PC and AA-PC correlated directly with MCA PI (p &lt; 0.05). In fetuses initially referred for inadequate fetal growth (EFW &lt; 10%), those with BW ≤ 5% demonstrated distinctly different cord plasma lipid profiles than those with BW &gt; 5%, which correlated with Doppler PIs. This provides new insights into fetal lipidomic response to the FGR in utero environment. The impact of these changes on specific processes of growth and development (particularly fetal brain) have not been elucidated, but the relationship with Doppler PI may provide additional context for FGR surveillance, and a more targeted approach to nutritional management of these infants.

Doppler Ultrasound of the Umbilical Artery: Clinical Application

OBJECTIVE

 To provide a survey of relevant literature on umbilical artery Doppler ultrasound use in clinical practice, technical considerations and limitations, and future perspectives.

METHODS

 Literature searches were conducted in PubMed and Medline, restricted to articles written in English. Additionally, the references of all analyzed studies were searched to obtain necessary information.

RESULTS

 The use of this technique as a routine surveillance method is only recommended for high-risk pregnancies with impaired placentation. Meta-analyses of randomized trials have established that obstetric management guided by umbilical artery Doppler findings can improve perinatal mortality and morbidity. The values of the indices of Umbilical artery Doppler decrease with advancing gestational age; however, a lack of consensus on reference ranges prevails.

CONCLUSION

 Important clinical decisions are based on the information obtained with umbilical artery Doppler ultrasound. Future efforts in research are imperative to overcome the current limitations of the technique.

A survey of current practice in reporting third trimester fetal biometry and Doppler in Australia and New Zealand

Introduction

Inconsistent reporting practices in third trimester ultrasound, the choice of reference charts in particular, have the potential to misdiagnose abnormal fetal growth. But this may lead to unnecessary anxiety and confusion amongst patients and clinicians and ultimately influence clinical management. Therefore, we sought to determine the extent of variability in choice of fetal biometry and Doppler reference charts and reporting practices in Australia and New Zealand.

Methods

Clinicians performing and/or reporting obstetric ultrasound were invited to answer questions about fetal biometry and Doppler charts in a web-based survey.

Results

At least four population-based charts are in current use. The majority of respondents (78%) report the percentile for known gestational age (GA) alongside measurements and 63% using a cut-off of estimated fetal weight (EFW) < 10^th percentile when reporting small for gestational age (SGA) and/or fetal growth restriction (FGR). The thresholds for the use of fetal and maternal Doppler in third trimester ultrasound varied in terms of the GA, EFW cut-off, and how measures were reported. The majority of respondents were not sure of which Doppler charts were used in their practice.

Conclusion

This survey revealed inconsistencies in choice of reference chart and reporting practices. The potential for misdiagnosis of abnormal fetal growth remains a significant issue.

The cerebroplacental ratio: association with maternal hypertension and proteinuria

Objective

To evaluate the resistive indices (RIs) of the fetal umbilical and middle cerebral arteries, as well as to determine the cerebroplacental ratio (CPR), in fetuses of women with hypertension.

Materials and Methods

This was a comparative cross-sectional study involving 75 pregnant women with pregnancy-induced hypertension (PIH) and 75 apparently healthy pregnant women (control group), all of whom were submitted to Doppler ultrasound examination of the fetal middle cerebral and umbilical arteries between 20 and 40 weeks of gestation. The two groups were compared in terms of the RI of the middle cerebral and umbilical arteries, as well as the CPR. The level of statistical significance was set at p ≤ 0.05.

Results

The mean age was 32.4 ± 4.6 years in the PIH group and 32.6 ± 4.6 years in the control group (p = 0.633). The mean umbilical artery RI was significantly higher in the PIH group than in the control group (0.67 ± 0.14 vs. 0.61 ± 0.08; p = 0.012), whereas the mean middle cerebral artery RI was significantly higher in the control group (0.80 ± 0.05 vs. 0.76 ± 0.08; p = 0.001). Among the women in the PIH group, the mean CPR was significantly lower for those with proteinuria than for those without (1.07 ± 0.26 vs. 1.27 ± 0.22; p = 0.001).

Conclusion

Maternal hypertension during pregnancy appears to be associated with increased fetal umbilical artery RI and reduced fetal middle cerebral artery RI, as well as with a low CPR. In pregnant women, the combination of PIH and proteinuria is also apparently associated with an increased risk of a low CPR.

Probing the ballistic microcirculation in placenta using flow-compensated and non-compensated intravoxel incoherent motion imaging

PURPOSE

Intravoxel incoherent motion (IVIM) imaging is widely used to evaluate microcirculatory flow, which consists of diffusive and ballistic flow components. We proposed a joint use of flow-compensated (FC) and non-compensated (NC) diffusion gradients to probe the fraction and velocity of ballistic flow in the placenta.

METHODS

Forty pregnant women were included in this study and scanned on a 1.5T clinical scanner. FC and NC diffusion MRI (dMRI) sequences were achieved using a pair of identical or mirrored bipolar gradients. A joint FC-NC model was established to estimate the fraction (f_b ) and velocity (v_b ) of the ballistic flow. Conventional IVIM parameters (f, D, and D*) were obtained from the FC and NC data, separately. The v_b and f·D*, as placental flow velocity measurements, were correlated with the umbilical-artery Doppler ultrasound indices and gestational ages.

RESULTS

The ballistic flow component can be observed from the difference between the FC and NC dMRI signal decay curves. v_b fitted from the FC-NC model showed strong correlations with umbilical-artery impedance indices, the systolic-to-diastolic (SD) ratio and pulsatility index (PI), with correlation coefficients of 0.65 and 0.62. The f·D* estimated from the NC data positively correlated with SD and PI, while the FC-based f·D* values showed weak negative correlations. Significant gestational-age dependence was also found in the flow velocity measurements.

CONCLUSION

Our results demonstrated the feasibility of using FC and NC dMRI to noninvasively measure ballistic flow velocity in the placenta, which may be used as a new marker to evaluate placenta microcirculation.

Peri-operative management of percutaneous fetoscopic spina-bifida repair: a descriptive review of five cases from the United Kingdom, with focus on anaesthetic implications

We present a case-based review of the first five percutaneous fetoscopic in-utero spina bifida repair procedures undertaken in the UK. Our focus is on implications of anaesthesia and analgesia for the mother and fetus, provision of uterine relaxation and fetal immobilisation while providing conditions conducive to surgical access. Minimising risks for fetal acidosis, placental and fetal hypoperfusion, maternal and fetal sepsis and maternal fluid overload were the foremost priorities. We discuss optimisation strategies undertaken to ensure fetal and maternal well-being under anaesthesia, shortcomings in the current approach, and possible directions for improvement.

Effect of sildenafil on maternal hemodynamics in pregnancies complicated by severe early-onset fetal growth restriction: planned subgroup analysis from a multicenter randomized placebo-controlled double-blind trial

OBJECTIVES

Fetal growth restriction (FGR) is associated with maternal cardiovascular changes. Sildenafil, a phosphodiesterase type-5 inhibitor, potentiates the actions of nitric oxide, and it has been suggested that it alters maternal hemodynamics, potentially improving placental perfusion. Recently, the Dutch STRIDER trial was stopped prematurely owing to excess neonatal mortality secondary to pulmonary hypertension. The main aim of this study was to investigate the effect of sildenafil on maternal hemodynamics in pregnancies with severe early-onset FGR.

METHODS

This was a cardiovascular substudy within a UK multicenter, placebo-controlled trial, in which 135 women with a singleton pregnancy and severe early-onset FGR (defined as a combination of estimated fetal weight or abdominal circumference below the 10^th centile and absent/reversed end-diastolic flow in the umbilical artery on Doppler velocimetry, diagnosed between 22 + 0 and 29 + 6 weeks' gestation) were assigned randomly to receive either 25 mg sildenafil three times daily or placebo until 32 + 0 weeks' gestation or delivery. Maternal blood pressure (BP), heart rate (HR), augmentation index, pulse wave velocity (PWV), cardiac output, stroke volume (SV) and total peripheral resistance were recorded before randomization, 1-2 h and 48-72 h post-randomization, and 24-48 h postnatally. For continuous data, analysis was performed using repeated measures ANOVA methods including terms for timepoint, treatment allocation and their interaction.

RESULTS

Included were 134 women assigned randomly to sildenafil (n = 69) or placebo (n = 65) who had maternal BP and HR recorded at baseline. At 1-2 h post-randomization, compared with baseline values, sildenafil increased maternal HR by 4 bpm more than did placebo (mean difference, 5.00 bpm (95% CI, 1.00-12.00 bpm) vs 1.25 bpm (95% CI, -5.38 to 7.88 bpm); P = 0.004) and reduced systolic BP by 1 mmHg more (mean difference, -4.13 mmHg (95% CI, -9.94 to 1.44 mmHg) vs -2.75 mmHg (95% CI, -7.50 to 5.25 mmHg); P = 0.048). Even after adjusting for maternal mean arterial pressure, sildenafil reduced aortic PWV by 0.60 m/s more than did placebo (mean difference, -0.90 m/s (95% CI, -1.31 to -0.51 m/s) vs -0.26 m/s (95% CI, -0.75 to 0.59 m/s); P = 0.001). Sildenafil was associated with a non-significantly greater decrease in SV index after 1-2 h post-randomization than was placebo (mean difference, -5.50 mL/m² (95% CI, -11.00 to -0.50 mL/m² ) vs 0.00 mL/m² (95% CI, -5.00 to 4.00 mL/m² ); P = 0.056).

CONCLUSIONS

Sildenafil in a dose of 25 mg three times daily increases HR, reduces BP and reduces arterial stiffness in pregnancies complicated by severe early-onset FGR. These changes are short term, modest and consistent with the anticipated vasodilatory effect. They have no short- or long-term clinical impact on the mother. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Nanoparticle Contrast-enhanced T1-Mapping Enables Estimation of Placental Fractional Blood Volume in a Pregnant Mouse Model

Non-invasive methods for estimating placental fractional blood volume (FBV) are of great interest for characterization of vascular perfusion in placentae during pregnancy to identify placental insufficiency that may be indicative of local ischemia or fetal growth restriction (FGR). Nanoparticle contrast-enhanced magnetic resonance imaging (CE-MRI) may enable direct placental FBV estimation and may provide a reliable, 3D alternative to assess maternal-side placental perfusion. In this pre-clinical study, we investigated if placental FBV at 14, 16, and 18 days of gestation could be estimated through contrast-enhanced MRI using a long circulating blood-pool liposomal gadolinium contrast agent that does not penetrate the placental barrier. Placental FBV estimates of 0.47 ± 0.06 (E14.5), 0.50 ± 0.04 (E16.5), and 0.52 ± 0.04 (E18.5) were found through fitting pre-contrast and post-contrast T1 values in placental tissue using a variable flip angle method. MRI-derived placental FBV was validated against nanoparticle contrast-enhanced computed tomography (CE-CT) derived placental FBV, where signal is directly proportional to the concentration of iodine contrast agent. The results demonstrate successful estimation of the placental FBV, with values statistically indistinguishable from the CT derived values.

Doppler ultrasound can be used to monitor umbilical arterial blood flow in lightly sedated pigs at multiple gestational ages

Doppler ultrasound was performed under moderate sedation (ketamine and azaperone) for 30min to monitor umbilical arterial (UA) blood flow in one uterine horn of Large White×Landrace gilts (n=23) at Gestational Days (GD) 30, 45, 60 and 90. Gilts were scanned before they were killed to examine relationships between litter size, sex ratio and five UA parameters (peak systolic velocity (PSV), end diastolic velocity (EDV), A/B (PSV to EDV) ratio, fetal heart rate (FHR) and resistance index (RI)). In gilts in which scans were obtained from all fetuses in the scanned horn, relationships between UA parameters, and fetal weight and sex were examined. A subset of gilts were sedated, scanned and recovered (SSR) earlier in gestation (GD30 or GD45) to assess the effects of sedation on later fetal development by comparison with control litters (no previous sedation). Temporal changes were observed in all UA parameters (P≤0.001). At GD60 and GD90, FHR decreased with increasing duration of sedation (P≤0.001). Sex ratio and fetal weight affected UA blood flow, whereas litter size and fetal sex did not. SSR at GD30 and GD45 was associated with decreased fetal weight at GD60 (P≤0.001) and GD90 (P=0.06) respectively, compared with controls. These results suggest maternal sedation during gestation affects fetal development, which should be investigated further. Measuring UA blood flow in growth-restricted porcine fetuses throughout gestation may be feasible.

The Impact of Infection in Pregnancy on Placental Vascular Development and Adverse Birth Outcomes

Healthy fetal development is dependent on nutrient and oxygen transfer via the placenta. Optimal growth and function of placental vasculature is therefore essential to support in utero development. Vasculogenesis, the de novo formation of blood vessels, and angiogenesis, the branching and remodeling of existing vasculature, mediate the development and maturation of placental villi, which form the materno-fetal interface. Several lines of evidence indicate that systemic maternal infection and consequent inflammation can disrupt placental vasculogenesis and angiogenesis. The resulting alterations in placental hemodynamics impact fetal growth and contribute to poor birth outcomes including preterm delivery, small-for-gestational age (SGA), stillbirth, and low birth weight (LBW). Furthermore, pathways involved in maternal immune activation and placental vascularization parallel those involved in normal fetal development, notably neurovascular development. Therefore, immune-mediated disruption of angiogenic pathways at the materno-fetal interface may also have long-term neurological consequences for offspring. Here, we review current literature evaluating the influence of maternal infection and immune activation at the materno-fetal interface and the subsequent impact on placental vascular function and birth outcome. Immunomodulatory pathways, including chemokines and cytokines released in response to maternal infection, interact closely with the principal pathways regulating placental vascular development, including the angiopoietin-Tie-2, vascular endothelial growth factor (VEGF), and placental growth factor (PlGF) pathways. A detailed mechanistic understanding of how maternal infections impact placental and fetal development is critical to the design of effective interventions to promote placental growth and function and thereby reduce adverse birth outcomes.

Fetal renal blood flow velocimetry and cerebro-placental ratio in patients with isolated oligohydramnios

OBJECTIVE

It's proposed that oligohydramnios is caused by decreased renal perfusion due to redistribution of fetal blood at fetal growth restriction. Isolated oligohydramnios refers to the presence of oligohydramnios without fetal structural and chromosomal abnormalities, without fetal growth restriction, without intrauterine infection, and in the absence of known maternal disease. It's unknown whether the redistribution or decreased renal perfusion cause isolated oligohydramnios. The aim of the study was to evaluate fetal renal artery Doppler blood velocimetry and cerebro-placental ratio (CPR) among women with isolated oligohydramnios between 25-40 weeks of gestational age.

STUDY DESIGN

The middle cerebral artery, umbilical artery and, renal artery pulsatility index (PI) values were measured in 45 fetuses with isolated oligohydramnios and 65 fetuses with normal amniotic fluid. Oligohydramnios was defined as deepest vertical amniotic fluid being measured lower than 1cm. The CPR (middle cerebral artery PI/umbilical artery PI) and renal artery PI values were expressed as multiples of the normal median (MoM) and were compared between the two groups.

RESULTS

There was no difference in MoM of CPR PI (p=0.167) and MoM of renal artery PI values (right p=0.253, left p=0.353) between the groups.

CONCLUSION

The renal artery Doppler velocimetry and CPR were not significantly different in the women with isolated oligohydramnios, compared to the women with normal amniotic fluid.

Concomitant intrauterine growth restriction alters the lipoprotein profile in preeclampsia

OBJECTIVE

Preeclampsia and intrauterine growth restriction (IUGR) are related conditions. We aimed to characterise common lipid changes.

METHODS

Triglyceride and cholesterol levels of patients 24-42 weeks of gestation with IUGR (n = 52), hypertensive IUGR (HIUGR, n = 28), and preeclampsia without IUGR (PE, n = 56) were compared to a control group (CTRL, n = 167). In addition, 60 sera (n = 10 of each pathology IUGR, HIUGR, PE (without IUGR) compared to n = 30 matched CTRL) of severe early onset cases <34 weeks of gestation were chosen and further analysed by ultracentrifugation lipid subfractionation including VLDL, IDL, LDL, and HDL composition.

RESULTS

In the full cohort we found low cholesterol in IUGR (p = 0.0405), while triglyceride levels were high in PE (p < 0.0001). Lipid concentrations in HIUGR did not differ significantly from CTRL. In the 60 patients analysed by lipid subfractionation, triglyceride levels were increased in the VLDL subfraction in PE (p < 0.01), however, LDL-bound ApoB and cholesterol levels were lower in IUGR and HIUGR (p < 0.0001 for total cholesterol and p < 0.001 for ApoB in both groups), but not in PE when compared to CTRL.

CONCLUSION

Low cholesterol, especially LDL cholesterol levels are a feature of IUGR while high triglyceride levels are a feature of preeclampsia. Increased VLDL-triglycerides suggest a disturbed conversion to LDL in preeclampsia. Of note, the presence of IUGR in hypertensive disorders further alters lipid profiles, which may explain heterogeneous data on lipid values for preeclampsia in the literature. Study groups have to be selected carefully to avoid misinterpretation.

A maternal meal affects clinical Doppler parameters in the fetal middle cerebral artery

INTRODUCTION

Middle cerebral artery (MCA) and umbilical artery (UA) Doppler blood flow pulsatility indices (PIs) and MCA peak systolic velocity (PSV) are essential variables for clinically evaluating fetal well-being. Here we examined how a maternal meal influenced these Doppler blood flow velocity variables.

METHODS

This prospective cohort study included 89 healthy Caucasian women with normal singleton pregnancies (median age, 32 years). Measurements were performed at gestational weeks 30 and 36, representing the start and near the end of the energy-depositing period. Measured variables included the MCA-PI, UA-PI, fetal heart rate (FHR) and MCA-PSV. The cerebroplacental ratio (CPR) was calculated as the ratio of MCA-PI to UA-PI. The first examination was performed in the fasting state at 08:30 a.m. Then participants ate a standard breakfast (approximate caloric intake, 400kcal), and the examination was repeated ~105 min after the meal.

RESULTS

Without adjustment for FHR, fetal MCA-PI decreased after the meal at week 30 (‒0.115; p = 0.012) and week 36 (‒0.255; p < 0.001). All PI values were negatively correlated with FHR. After adjustment for FHR, MCA-PI still decreased after the meal at week 30 (‒0.087; p = 0.044) and week 36 (‒0.194; p < 0.001). The difference between the two gestational weeks was non-significant (p = 0.075). UA-PI values did not significantly change at week 30 (p = 0.253) or week 36 (p = 0.920). CPR revealed significant postprandial decreases of -0.17 at week 30 (p = 0.006) and -0.22 at week 36 (p = 0.001). Compared to fasting values, MCA-PSV was significantly higher after food intake: +3.9 cm/s at week 30 (p < 0.001) and +5.9 cm/s at week 36 (p < 0.001).

CONCLUSION

In gestational weeks 30 and 36, we observed a postprandial influence that was apparently specific to fetal cerebral blood flow.

Simultaneous umbilical blood flow during normal pregnancy in sheep and goat foetuses using non-invasive colour Doppler ultrasound

The characteristics of umbilical blood flow (UM) was investigated using 18 (25 foetuses) pregnant ewes and 20 (41 foetus) pregnant goats transrectal non-invasive color Doppler ultrasonographic examinations were done frequently between 2 and 8 week after breeding and then transabdominally until parturition. Colour Doppler velocimetery includes blood flow volume (BFV), time averaged maximum velocity (TAMV), resistance index (RI), pulsatility index (PI), time average of mean (TAMEAN) and impedance of blood flow (PS/ED or AB ratio). Also a qualitative evaluation of UM blood flow indicating increases (P < 0.001) in BFV, TAMV and TAMEAN were observed until 19 week of pregnancy in foetuses of sheep and goats and then those values decreased (P < 0.001) from 19 week until parturition. Conversely, UM-PI, RI and PS/ED decreased (P < 0.002-0.01) until 19 week and then increased (P < 0.01-0.0001). The umbilical artery BFV increased (P < 0.0001) during pregnancy from 7.27 ± 0.82 ml/min in sheep vs. 4.96 ± 0.54 ml/min in goats at 6 week of gestation to 700.51 ± 31.05 ml/min (~100 fold) in sheep vs. 665.56 ± 48.22 ml/min (~133 fold) in goats at 19 week and then decreased (P < 0.0001) to 350.561 ± 72.15 ml/min in sheep vs. 215.17 ± 35.06 ml/min in goats at 20 week. The absence of end diastolic velocity (EDV) of umbilical artery blood flow was detected in both species between 4 and 12 week of pregnancy. Results of this study clearly show that the non-invasive colour Doppler sonography can be used successfully to assess umbilical blood flow in foetuses of pregnant sheep and goats. These may provide guidelines for assessing the state of intrauterine fetal growth retardation in pregnancies of sheep and goats.

Near to One's Heart: The Intimate Relationship Between the Placenta and Fetal Heart

The development of the fetal heart is exquisitely controlled by a multitude of factors, ranging from humoral to mechanical forces. The gatekeeper regulating many of these factors is the placenta, an external fetal organ. As such, resistance within the placental vascular bed has a direct influence on the fetal circulation and therefore, the developing heart. In addition, the placenta serves as the interface between the mother and fetus, controlling substrate exchange and release of hormones into both circulations. The intricate relationship between the placenta and fetal heart is appreciated in instances of clinical placental pathology. Abnormal umbilical cord insertion is associated with congenital heart defects. Likewise, twin-to-twin transfusion syndrome, where monochorionic twins have unequal sharing of their placenta due to inter-twin vascular anastomoses, can result in cardiac remodeling and dysfunction in both fetuses. Moreover, epidemiological studies have suggested a link between placental phenotypic traits and increased risk of cardiovascular disease in adult life. To date, the mechanistic basis of the relationships between the placenta, fetal heart development and later risk of cardiac dysfunction have not been fully elucidated. However, studies using environmental exposures and gene manipulations in experimental animals are providing insights into the pathways involved. Likewise, surgical instrumentation of the maternal and fetal circulations in large animal species has enabled the manipulation of specific humoral and mechanical factors to investigate their roles in fetal cardiac development. This review will focus on such studies and what is known to date about the link between the placenta and heart development.

Endothelial indoleamine 2,3-dioxygenase-1 regulates the placental vascular tone and is deficient in intrauterine growth restriction and pre-eclampsia

Indoleamine 2,3-dioxygenase-1 (IDO1) mediates the degradation of L-tryptophan (L-Trp) and is constitutively expressed in the chorionic vascular endothelium of the human placenta with highest levels in the microvasculature. Given that endothelial expression of IDO1 has been shown to regulate vascular tone and blood pressure in mice under the condition of systemic inflammation, we asked whether IDO1 is also involved in the regulation of placental blood flow and if yes, whether this function is potentially impaired in intrauterine growth restriction (IUGR) and pre-eclampsia (PE). In the large arteries of the chorionic plate L-Trp induced relaxation only after upregulation of IDO1 using interferon gamma and tumor necrosis factor alpha. However, ex vivo placental perfusion of pre-constricted cotyledonic vasculature with L-Trp decreases the vessel back pressure without prior IDO1 induction. Further to this finding, IDO1 protein expression and activity is reduced in IUGR and PE when compared to gestational age–matched control tissue. These data suggest that L-Trp catabolism plays a role in the regulation of placental vascular tone, a finding which is potentially linked to placental and fetal growth. In this context our data suggest that IDO1 deficiency is related to the pathogenesis of IUGR and PE.

Simultaneous Ablation of Uterine Natural Killer Cells and Uterine Mast Cells in Mice Leads to Poor Vascularization and Abnormal Doppler Measurements That Compromise Fetal Well-being

Intrauterine growth restriction (IUGR) is a serious pregnancy complication with short- and long-term health consequences. The mechanisms underlying this condition are not well understood. Animal models are the basis for understanding the causes of IUGR and for developing useful therapeutic strategies. Here, we aimed to ascertain the in utero growth of fetuses from NK (natural killer cells)/MC (mast cells)-deficient mothers that give birth to growth-restricted pups and to determine the time point at which IUGR starts. We used high frequency ultrasound imaging to follow-up fetal and placenta size and employed Doppler measurements to document blood supply to the fetus in females that were deficient for NK cells and MCs. In mice lacking NKs and MCs, we observed significantly reduced implantation sizes from mid gestation onward, which was further associated with smaller placentas. Additionally, NK/MC-deficiency was associated with absent and reversed end diastolic flow in umbilical arteries of the fetuses and an increased systolic/diastolic ratio as well as an elevated resistance index. Together, our results indicate that NKs/MCs promote blood flow, placental growth, and subsequent fetal development. The results of this study offer new insights as to how fetal growth is affected in vivo in NK/MC-deficient mice, whose pups are growth restricted at birth. The use of IUGR models and modern technologies enabling the in vivo follow-up of fetal development are important tools for understanding mechanisms behind pregnancy complications that in the future may lead to the development of effective therapies.

Molecular and cellular underpinnings of normal and abnormal human placental blood flows

Abnormal placental function is well-established as a major cause for poor pregnancy outcome. Placental blood flow within the maternal uteroplacental compartment, the fetoplacental circulation or both is a vital factor in mediating placental function. Impairment in flow in either or both vasculatures is a significant risk factor for adverse pregnancy outcome, potentially impacting maternal well-being, affecting immediate neonatal health and even influencing the long-term health of the infant. Much remains unknown regarding the mechanistic underpinnings of proper placental blood flow. This review highlights the currently recognized molecular and cellular mechanisms in the development of normal uteroplacental and fetoplacental blood flows. Utilizing the entities of preeclampsia and fetal growth restriction as clinical phenotypes that are often evident downstream of abnormal placental blood flow, mechanisms underlying impaired uteroplacental and fetoplacental blood flows are also discussed. Deficiencies in knowledge, which limit the efficacy of clinical care, are also highlighted, underscoring the need for continued research on normal and abnormal placental blood flows.

Fetal and umbilical Doppler ultrasound in high-risk pregnancies

BACKGROUND

Abnormal blood flow patterns in fetal circulation detected by Doppler ultrasound may indicate poor fetal prognosis. It is also possible that false positive Doppler ultrasound findings could lead to adverse outcomes from unnecessary interventions, including preterm delivery.

OBJECTIVES

The objective of this review was to assess the effects of Doppler ultrasound used to assess fetal well-being in high-risk pregnancies on obstetric care and fetal outcomes.

SEARCH METHODS

We updated the search of Cochrane Pregnancy and Childbirth's Trials Register on 31 March 2017 and checked reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of Doppler ultrasound for the investigation of umbilical and fetal vessels waveforms in high-risk pregnancies compared with no Doppler ultrasound. Cluster-randomised trials were eligible for inclusion but none were identified.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Nineteen trials involving 10,667 women were included. Risk of bias in trials was difficult to assess accurately due to incomplete reporting. None of the evidence relating to our main outcomes was graded as high quality. The quality of evidence was downgraded due to missing information on trial methods, imprecision in risk estimates and heterogeneity. Eighteen of these studies compared the use of Doppler ultrasound of the umbilical artery of the unborn baby with no Doppler or with cardiotocography (CTG). One more recent trial compared Doppler examination of other fetal blood vessels (ductus venosus) with computerised CTG.The use of Doppler ultrasound of the umbilical artery in high-risk pregnancy was associated with fewer perinatal deaths (risk ratio (RR) 0.71, 95% confidence interval (CI) 0.52 to 0.98, 16 studies, 10,225 babies, 1.2% versus 1.7 %, number needed to treat (NNT) = 203; 95% CI 103 to 4352, evidence graded moderate). The results for stillbirths were consistent with the overall rate of perinatal deaths, although there was no clear difference between groups for this outcome (RR 0.65, 95% CI 0.41 to 1.04; 15 studies, 9560 babies, evidence graded low). Where Doppler ultrasound was used, there were fewer inductions of labour (average RR 0.89, 95% CI 0.80 to 0.99, 10 studies, 5633 women, random-effects, evidence graded moderate) and fewer caesarean sections (RR 0.90, 95% CI 0.84 to 0.97, 14 studies, 7918 women, evidence graded moderate). There was no comparative long-term follow-up of babies exposed to Doppler ultrasound in pregnancy in women at increased risk of complications.No difference was found in operative vaginal births (RR 0.95, 95% CI 0.80 to 1.14, four studies, 2813 women), nor in Apgar scores less than seven at five minutes (RR 0.92, 95% CI 0.69 to 1.24, seven studies, 6321 babies, evidence graded low). Data for serious neonatal morbidity were not pooled due to high heterogeneity between the three studies that reported it (1098 babies) (evidence graded very low).The use of Doppler to evaluate early and late changes in ductus venosus in early fetal growth restriction was not associated with significant differences in any perinatal death after randomisation. However, there was an improvement in long-term neurological outcome in the cohort of babies in whom the trigger for delivery was either late changes in ductus venosus or abnormalities seen on computerised CTG.

AUTHORS' CONCLUSIONS

Current evidence suggests that the use of Doppler ultrasound on the umbilical artery in high-risk pregnancies reduces the risk of perinatal deaths and may result in fewer obstetric interventions. The results should be interpreted with caution, as the evidence is not of high quality. Serial monitoring of Doppler changes in ductus venosus may be beneficial, but more studies of high quality with follow-up including neurological development are needed for evidence to be conclusive.

Developmental Changes in Aortic Mechanical Properties in Normal Fetuses and Fetuses with Cardiovascular Disease

BACKGROUND

We hypothesized that fetal aortic mechanical properties assessed by aortic diameter (AoD) and flow show maturational changes during the gestational period, and that these properties are different in fetuses with congenital heart diseases and fetuses with normal development.

METHODS

Phasic changes in ascending AoD along with Doppler flow profile were measured in 84 consecutive normal fetuses (gestational age, 18-36 weeks) and in 30 consecutive fetuses with cardiovascular diseases (gestational age, 22-39 weeks).

RESULTS

AoD and cardiac output significantly increased with gestational age. Fetal aortic compliance (AC), assessed as (maximum AoD - minimum AoD)/stroke volume, significantly decreased with gestational age in normal fetuses, indicating maturational changes in aortic wall properties. Importantly, fetuses with Marfan syndrome and tetralogy of Fallot that exhibit "aortopathy" showed significantly lower AC than normal fetuses of the same gestational age, suggesting intrinsic abnormalities in aortic wall properties in these diseases. Fetuses with trisomy 18 and Noonan syndrome also had AC values below the normal ranges.

CONCLUSION

Measurements of phasic changes in fetal AoD and flow measurements can provide useful information about aortic mechanical properties and may help clarify abnormal arterial hemodynamics in pathologic conditions.

Oxidative stress, placental ageing-related pathologies and adverse pregnancy outcomes

Oxidative stress (OS), an imbalance between free radical generation and antioxidant defence, is recognized as a key factor in the pathogenesis of adverse pregnancy outcomes. Although OS is a common future of normal pregnancy, persistent, overwhelming OS leads to consumption and decline of antioxidants, affecting placental antioxidant capacity and reducing systems. The accumulation of OS causes damage to lipids, proteins and DNA in the placental tissue that induces a form of accelerated ageing. Premature ageing of the placenta is associated with placental insufficiency that prevents the organ meeting the needs of the foetus, and as a consequence, the viability of the foetus is compromised. This review summarizes the literature regarding the role of OS and premature placental ageing in the pathophysiology of pregnancy complications.

Effects of Oxygen Tension and Normalization Pressure on Endothelin-Induced Constriction of Human Placental Chorionic Plate Arteries

OBJECTIVES

Fetoplacental blood vessels constrict in response to endothelin (ET-1) or reduced oxygen tension in the placental cotyledon perfused in vitro. In nonplacental resistance arteries, hypoxia and ET-1 induce constriction by promoting Ca2+ influx into smooth muscle through membrane ion channels, which include voltage-gated Ca2+ channels (VGCCs). We hypothesized that VGCCs are involved in ET-1-induced constriction of fetoplacental resistance vessels and that their contribution to constriction is enhanced at low oxygen tension.

METHODS

Chorionic plate small arteries from term placentas were studied using parallel wire myography. Arteries were normalized at 0.9 of L(5.1 kPa) ("low stretch" approximately 25 mm Hg; approximating physiologic vascular pressure) or 0.9 of L(13.3 kPa) ("high stretch" approximately 42 mm Hg) and experiments performed at oxygen tensions of 156, 38, and 15 mm Hg.

RESULTS

When chorionic plate arteries were normalized at low stretch, oxygen tension did not affect constriction to ET-1. Nifedipine (10(-4) M), a blocker of L-type VGCCs, inhibited ET-1 (EC80)-induced constriction to a similar extent at each oxygen tension (52% to 64% inhibition). In contrast, when arteries were normalized at high stretch, constriction to ET-1 was greater at 38 than at 156 or 15 mm Hg oxygen and nifedipine inhibition of ET-1-induced constriction was greater at 38 and 15 mm Hg than at 156 mm Hg oxygen.

CONCLUSIONS

VGCCs and nifedipine-insensitive processes underlie the contractile response of chorionic plate arteries to ET-1 and their relative contribution to vasoconstriction is modulated by oxygen tension when vessels are normalized at high stretch. However, contrary to our hypothesis, the response of chorionic plate arteries to ET-1 is not modulated by oxygen when vessels are normalized at physiologic pressure.

Use of conditional centiles of middle cerebral artery pulsatility index and cerebroplacental ratio in the prediction of adverse perinatal outcomes

INTRODUCTION

Centiles of middle cerebral artery pulsatility index and cerebroplacental ratio are useful for predicting adverse perinatal outcomes. A 'conditional centile' is conditioned by a previous measurement reflecting degree of individual change over time. Here we test whether such centiles are independent predictors and whether their combination improves prediction.

MATERIAL AND METHODS

This prospective longitudinal study included 220 pregnant women diagnosed with or at risk of having a small-for-gestational-age fetus. Serial Doppler measurements of the umbilical artery and middle cerebral artery pulsatility indexs were used to calculate cerebroplacental ratio. Preterm birth, operative delivery due to fetal distress, admission to neonatal intensive care unit, 5-min Apgar score <7, newborn hypoglycemia, and perinatal mortality were considered adverse outcomes. Possible associations were analyzed by log-binomial regression analysis.

RESULTS

Serial Doppler measurements of the middle cerebral artery were available in 207 participants and cerebroplacental ratio in 205. Conditional centiles ≤5 and ≤10 for both middle cerebral artery pulsatility index and cerebroplacental ratio were associated with increased risk for adverse perinatal outcomes. However, only the combination of cerebroplacental ratio centile and conditional centile ≤10 showed a better performance in the prediction of operative delivery due to fetal distress (p = 0.032), admission to neonatal intensive care unit (p = 0.048), and the combined variable "any adverse outcomes" (p = 0.034) compared with the use of centile ≤10 alone.

CONCLUSIONS

Conditional centile for middle cerebral artery pulsatility index and cerebroplacental ratio ≤5 and ≤10 are associated with adverse perinatal outcomes. When adding conditional centile to conventional centile for cerebroplacental ratio, the prediction improved compared with the use of conventional centile alone.

Neurodevelopmental outcome in very low birthweight infants with pathological umbilical artery flow

OBJECTIVE

To assess neurodevelopmental outcome during toddlerhood in very low birthweight (VLBW) infants with absent or reverse end-diastolic flow (AREDF) in the umbilical artery (UA) during pregnancy.

DESIGN

Retrospective cohort study with matched control group.

SETTING

Tertiary perinatal centre.

PATIENTS AND OUTCOME MEASURES

We compared longitudinally collected data on neonatal and neurodevelopmental outcomes among 41 infants born in our institution from 1997 to 2010 with birth weight <1500 g and UA AREDF and 41 infants with prenatally normal UA Doppler parameters matched for gestational age, birth weight, sex and year of birth. We evaluated neurodevelopmental outcome at a median (range) corrected age of 23.3 (10.1-29.6) months using the Bayley scales of infant development, 2nd edition (BSID-II), and neurological examination.

RESULTS

The mental development index in UA AREDF children (median (range) 84 (49-116)) was significantly lower than in controls (median (range) 91 (62-140)), including after adjustment for confounders. Intergroup differences in psychomotor development index (PDI; BSID-II) and the rate of cerebral palsy or minor neuromotor dysfunction were non-significant.

CONCLUSIONS

VLBW infants with UA AREDF have a higher risk of poorer mental development during toddlerhood than controls matched for gestational age, birth weight, sex and year of birth. UA AREDF may be considered a prenatal predictor of poorer mental development in this population. Long-term follow-up studies with larger cohorts are needed to better evaluate the impact of this prenatal factor on later neurodevelopment.

Progesterone suppressed vasoconstriction in human umbilical vein via reducing calcium entry

The aim of this study was to evaluate the actions of progesterone on human umbilical vein (HUV) from normal pregnancies and the possible underlying mechanisms involved. HUV rings were suspended in organ baths and exposed to progesterone followed by phenylephrine (PE) or serotonin (5-HT). Progesterone suppressed PE- or 5-HT-induced vasoconstriction in HUV rings. The inhibitory effect induced by progesterone was not influenced by nitric oxide syntheses inhibitor, prostaglandins syntheses blocker, the integrity of endothelium, selective progesterone receptor or potassium channel antagonists. Further testing showed that progesterone and nifedipine (a blocker for L-type calcium channels) produced similar inhibitory effects on PE-, 5-HT-, Bay-k8644-, KCl-induced vasoconstriction in Krebs solution as well as CaCl2-induced vasoconstriction in Ca(2+)-free Krebs solution. But the inhibitory effect of mibefradil (mibe, a blocker for L-type (CaV1.2) and T-type calcium channels (CaV3.2)) on PE-, 5-HT-induced vasoconstriction was significantly greater than progesterone or nifedipine in Krebs solution. Furthermore, progesterone did not affect the vasoconstriction caused by PE, 5-HT, or caffeine in Ca(2+)-free Krebs solution. In addition, incubation HUV with progesterone did not change CaV1.2 and progesterone receptor (PR) expressions. The results gained demonstrated that progesterone could suppress multiple agonist-induced vasoconstrictions in HUV, mainly due to a reduction of calcium entry through L-type calcium channels, not endothelium-dependent vascular relaxation pathways, potassium channels, or Ca(2+) release from intracellular stores, providing new information important to further understanding the contribution of progesterone in the regulation of the placental-fetal circulation.

Ex Vivo Human Placental Perfusion Model for Analysis of Fetal Circulation in the Chorionic Plate

OBJECTIVES

The purpose of this study was to develop an ex vivo placental perfusion model to assess changes in the umbilical artery systolic-to-diastolic (S/D) ratio due to progressive occlusion of the placental arterial system.

METHODS

Ex vivo human placentas were connected to a computerized pulse duplicator mimicking pulsatile flow from the fetal heart. Doppler sonographic measurements were conducted on the umbilical and chorionic arteries of 25 mature placentas. Simulation of placental occlusion was performed by progressive ligature of the chorionic arteries, including one umbilical artery. The correlation between the umbilical artery S/D ratio and the severity of simulated placental occlusion was analyzed.

RESULTS

The normal mean S/D ratio ± SD decreased gradually along the chorionic plate from 2.66 ± 0.47 at the cord insertion to 1.90 ± 0.59 in generation IV of the chorionic vessels. The Doppler index initially increased slowly with simulated placental occlusion. Only when all 4 generations were occluded was the umbilical artery S/D ratio elevated. Complete occlusion of one umbilical artery resulted in a 39% increase in the umbilical artery S/D ratio.

CONCLUSIONS

This unique model combining Doppler sonography with perfusion of an ex vivo placenta can be used for a better understudying of pathologic placental blood flow circulation.

A longitudinal study of placental perfusion using dynamic contrast enhanced magnetic resonance imaging in murine pregnancy

INTRODUCTION

To evaluate changes in placental perfusion with advancing gestation in normal murine pregnancy using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI).

METHODS

Seven timed-pregnant CD-1 mice underwent DCE-MRI scanning longitudinally on gestational days (GD) 13, 15 and 17. Placentas were segmented into high (HPZ) and low perfusion zones (LPZ) using tissue similarity mapping. Blood perfusion of the respective regions and the whole placenta was quantified using the steepest slope method. The diameter of the maternal central canal (CC) was also measured.

RESULTS

An increase in perfusion was observed between GD13 and GD17 in the overall placenta (p = 0.04) and in the HPZ (p = 0.02). Although perfusion in the LPZ showed a slight increasing trend, it was not significant (p = 0.07). Perfusion, in units of ml/min/100 ml, in the overall placenta and the HPZ was respectively 61.2 ± 31.2 and 106.2 ± 56.3 at GD13 (n = 19 placentas); 90.3 ± 43.7 and 139 ± 55.4 at GD15 (n = 20); and 104.9 ± 76.1 and 172.2 ± 85.6 at GD17 (n = 14). The size of the CC increased with advancing gestation (p < 0.05).

DISCUSSION

Using longitudinal DCE-MRI, the gestational age-dependent perfusion change in the normal murine placenta and in its regional compartments was quantified. In mid and late gestations, placental constituent regions differ significantly in their perfusion rates. The CC diameter also showed increase with advancing gestation, which may be playing an important role toward the gestational age-dependent increase in placental perfusion.

Role of the fetoplacental endothelium in fetal growth restriction with abnormal umbilical artery Doppler velocimetry

Growth-restricted fetuses with absent or reversed end-diastolic velocities in the umbilical artery are at substantially increased risk for adverse perinatal and long-term outcome, even in comparison to growth-restricted fetuses with preserved end-diastolic velocities. Translational studies show that this Doppler velocimetry correlates with fetoplacental blood flow, with absent or reversed end-diastolic velocities signifying abnormally elevated resistance within the placental vasculature. The fetoplacental vasculature is unique in that it is not subject to autonomic regulation, unlike other vascular beds. Instead, humoral mediators, many of which are synthesized by local endothelial cells, regulate placental vascular resistance. Existing data demonstrate that in growth-restricted pregnancies complicated by absent or reversed umbilical artery end-diastolic velocities, an imbalance in production of these vasoactive substances occurs, favoring vasoconstriction. Morphologically, placentas from these pregnancies also demonstrate impaired angiogenesis, whereby vessels within the terminal villi are sparsely branched, abnormally thin, and elongated. This structural deviation from normal placental angiogenesis restricts blood flow and further contributes to elevated fetoplacental vascular resistance. Although considerable work has been done in the field of fetoplacental vascular development and function, much remains unknown about the mechanisms underlying impaired development and function of the human fetoplacental vasculature, especially in the context of severe fetal growth restriction with absent or reversed umbilical artery end-diastolic velocities. Fetoplacental endothelial cells are key regulators of angiogenesis and vasomotor tone. A thorough understanding of their role in placental vascular biology carries the significant potential of discovering clinically relevant and innovative approaches to prevention and treatment of fetal growth restriction with compromised umbilical artery end-diastolic velocities.

Effects of maternal abdominal decompression on umbilical artery and fetal middle cerebral artery blood flow

Introduction: Maternal abdominal decompression during pregnancy could be used in an attempt to improve utero-placental blood flow. We utilized Doppler ultrasonography to investigate the effects of this procedure on blood flow in the umbilical artery and fetal middle cerebral artery. Methods: Women (n = 23) with singleton pregnancies attending antenatal abdominal decompression were enrolled in the study. Doppler velocity waveforms were obtained from umbilical artery and fetal middle cerebral artery before and after a 30-minute decompression session. Resistance indices were compared using the Student's t - test (p < 0.05 significant). Results: 23 healthy pregnant women were included at an average gestational age of 36+1 weeks. The mean resistance index before decompression in the umbilical artery was 0.58 (s = 0.10) and after decompression 0.54 (s = 0.07, p = 0.06). In the middle cerebral artery the values were 0.72 (s = 0.11) and 0.77 (s = 0.08), respectively (p = 0.01). Discussion and conclusion: Significantly increased resistance index in the middle cerebral artery implies a higher fetal brain oxygenation after decompression. This is further corroborated by the trend towards a decrease in umbilical artery resistance index. The effects of decompression could be beneficial in pregnancies complicated by IUGR or hypertensive disorders of pregnancy.

Impact of maternal obesity on fetal programming of cardiovascular disease

The in utero environment is a key determinant of long-term health outcomes; poor maternal metabolic state and placental insufficiency are strongly associated with these long-term health risks. Human epidemiological studies link maternal obesity and offspring cardiovascular disease in later life, but mechanistic studies in animal models are limited. Here, we review the literature pertaining to maternal consequences of obesity during pregnancy and the subsequent impact on fetal cardiovascular development.

Oxygen sensitivity, potassium channels, and regulation of placental vascular tone

The human fetoplacental vasculature is a low-resistance circulation with deoxygenated arterial relative to venous blood. The placenta lacks neuronal innervation suggesting that local physical (e.g., oxygenation; flow rate), paracrine (e.g., endothelial cell nitric oxide), and circulating (e.g., angiotensin II) factors will contribute to blood flow regulation in small fetoplacental vessels. Oxygenation (specifically hypoxia) has received particular attention. At the macro-level, hypoxic challenge increases vascular resistance, but the data's physiological relevance remains questionable. K(+) channels are a diverse family of proteins known to play important roles in the normal physiological functions of endothelial and smooth muscle cells of a variety of vascular beds. K(+) channels are categorized by their predicted transmembrane structure or gating properties. A small number of perfused placental cotyledon and isolated blood vessels studies have assessed K(+) channel activity. Specific activator/inhibitor application suggests functional voltage-gated channels, whereas toxin inhibitor studies have documented KCa channel activity. Pharmacological KATP channel activation significantly dilates preconstricted placental arteries and veins. There is a paucity of cell subtype-specific expression studies of placental K(+) channels. This review focuses on the roles of K(+) channels and oxygenation in controlling reactivity of small fetoplacental blood vessels.

Uteroplacental circulation and fetal vascular function and development

Although blood flow in the placental vasculature is governed by the same physiological forces of shear, pressure and resistance as in other organs, it is also uniquely specialized on the maternal and fetal sides. At the materno-fetal interface, the independent uteroplacental and umbilicoplacental circulations must coordinate sufficiently to supply the fetus with the nutrients and substrates it needs to grow and develop. Uterine arterial flow must increase dramatically to accommodate the growing fetus. Recent evidence delineates the hormonal and endothelial mechanisms by which maternal vessels dilate and remodel during pregnancy. The umbilical circulation is established de novo during embryonic development but blood does not flow through the placenta until late in the first trimester. The umbilical circulation operates in the interest of maintaining fetal oxygenation over the course of pregnancy, and is affected differently by mechanical and chemical regulators of vascular tone compared to other organs. The processes that match placental vascular growth and fetal tissue growth are not understood, but studies of compromised pregnancies provide clues. The subtle changes that cause the failure of the normally regulated vascular processes during pregnancy have not been thoroughly identified. Likewise, practical and effective therapeutic strategies to reverse detrimental placental perfusion patterns have yet to be investigated.

A cohort study of Plasmodium falciparum malaria in pregnancy and associations with uteroplacental blood flow and fetal anthropometrics in Kenya

OBJECTIVE

To use ultrasound to explore the impact of malaria in pregnancy on fetal growth and newborn outcomes among a cohort of women enrolled in an intermittent presumptive treatment in pregnancy (IPTp) with sulfadoxine/pyrimethamine (SP) program in coastal Kenya.

METHODS

Enrolled women were tested for malaria at first prenatal care visit, and physical and ultrasound examinations were performed. In total, 477 women who had term, live births had malaria tested at delivery and their birth outcomes assessed, and were included in the study.

RESULTS

Peripheral malaria was detected via polymerase chain reaction among 10.9% (n=87) at first prenatal care visit and 8.8% (n=36) at delivery. Insecticide-treated bed nets (ITNs) were used by 73.6% (n=583) and were associated with decreased malaria risk. There was a trend for impaired fetal growth and placental blood flow in malaria-infected women in the second trimester, but not later in pregnancy. Among women with low body mass index (BMI), malaria was associated with reduced birth weight (P=0.04); anthropometric measures were similar otherwise.

CONCLUSION

With IPTp-SP and ITNs, malaria in pregnancy was associated with transient differences in utero, and reduced birth weight was restricted to those with low BMI.

Neuroendocrinology of pregnancy and parturition

During pregnancy, the maternal brain drives a series of adaptive mechanisms that are fundamental for allowing fetal growth and development, protecting both mother and fetus from adverse programming and timing of parturition. This neuroendocrine concept is even more complex as fetal brain and placenta also participate as regulators of maternal-placental-fetal physiology. The placenta is now seen as a neuroendocrine organ, acting as a source of several neuroactive factors that may exert their biologic effects either locally or by entering maternal and fetal circulation, thus acting in an autocrine, paracrine, and endocrine manner. A variety of hypothalamic neurohormones (GnRH, GHRH, somatostatin, CRH, oxytocin) are expressed in the placenta. When stress occurs during pregnancy, the maternal, fetal, and placental hypothalamic-pituitary-adrenal (HPA) axes are activated to stimulate a series of responses contributing to maintain physiologic conditions while at the same time avoiding the adverse effects of stress on the mother and offspring. However, when stress is excessive, a number of obstetric complications may occur, such as preterm birth, pre-eclampsia and intrauterine growth restriction, related to an impairment of the placental adaptive response.