Pathology and clinical implications of abnormal umbilical artery Doppler waveforms

A review of feto-placental vasculature flow modelling

The placenta provides the vital nutrients and removal of waste products required for fetal growth and development. Understanding and quantifying the differences in structure and function between a normally functioning placenta compared to an abnormal placenta is vital to provide insights into the aetiology and treatment options for fetal growth restriction and other placental disorders. Computational modelling of blood flow in the placenta allows a new understanding of the placental circulation to be obtained. This structured review discusses multiple recent methods for placental vascular model development including analysis of the appearance of the placental vasculature and how placental haemodynamics may be simulated at multiple length scales.

Angiogenic Function of Human Placental Endothelial Cells in Severe Fetal Growth Restriction Is Not Rescued by Individual Extracellular Matrix Proteins

Severe fetal growth restriction (FGR) is characterized by increased placental vascular resistance resulting from aberrant angiogenesis. Interactions between endothelial cells (ECs) and the extracellular matrix (ECM) are critical to the complex process of angiogenesis. We have previously found that placental stromal abnormalities contribute to impaired angiogenesis in severe FGR. The objective of this research is to better characterize the effect of individual ECM proteins on placental angiogenic properties in the setting of severe FGR. ECs were isolated from human placentae, either control or affected by severe FGR, and subjected to a series of experiments to interrogate the role of ECM proteins on adhesion, proliferation, migration, and apoptosis. We found impaired proliferation and migration of growth-restricted ECs. Although individual substrates did not substantially impact migratory capacity, collagens I, III, and IV partially mitigated proliferative defects seen in FGR ECs. Differences in adhesion and apoptosis between control and FGR ECs were not evident. Our findings demonstrate that placental angiogenic defects that characterize severe FGR cannot be explained by a singular ECM protein, but rather, the placental stroma as a whole. Further investigation of the effects of stromal composition, architecture, stiffness, growth factor sequestration, and capacity for remodeling is essential to better understand the role of ECM in impaired angiogenesis in severe FGR.

Prediction Model Assessing Risk of Delivery after Diagnosis of Abnormal Umbilical Artery Doppler

OBJECTIVE

Umbilical artery Doppler (UAD) velocimetry abnormalities are associated with increased neonatal morbidity and mortality. Currently, there are no risk stratification methods to assist in antepartum management such as timing of antenatal corticosteroids (ACS). Therefore, we sought to develop a model to predict risk of delivery within 7 days following diagnosis of abnormal UAD velocimetry in patients with fetal growth restriction (FGR).

STUDY DESIGN

Retrospective single referral center study of liveborn singleton pregnancies complicated by FGR and ≥1 abnormal UAD velocimetry value (≥95th percentile for gestational age [GA]). We considered 17 variables and used backward stepwise logistic regression to create a multivariable model for the prediction of delivery within 7 days. We assessed model fit with calibration, discrimination, likelihood ratios, and area under the curve. Internal validation of the model was assessed by using the bootstrap method.

RESULTS

Between 2008 and 2015, a total of 176 patients were eligible and included for model development. Median (range) GA at initial eligibility was 32.1 weeks (28.1-36.1 weeks) and from initial eligibility until delivery was 21 days (0-104 days). Fifty-two patients (30%) were delivered in the 7 days following inclusion. GA at first abnormal UAD, severity of first abnormal UAD, oligohydramnios, preeclampsia, and pre-pregnancy BMI were included in the model. The model had an area under the ROC curve of 0.94 (95% confidence interval [CI]: 0.90-0.98), sensitivity of 85%, and specificity of 91%. If the model alone were used for ACS timing, 85% of the cohort who delivered in the following week would have received ACS, and ACS would not have been given to 91% who delivered later. Internal validation yielded similar results with a mean area under the curve (95% CI) of 0.94 (0.88-0.98).

CONCLUSION

If validated externally, our model can be used to predict risk of delivery in patients with FGR and abnormal UAD velocimetry, potentially improving timing of ACS.

KEY POINTS

· Risk of delivery in seven days can be predicted.. · Risk of delivery can inform corticosteroid timing.. · External validation can further develop a clinical aid..

Mechanistic insights into the development of severe fetal growth restriction

Fetal growth restriction (FGR), which most commonly results from suboptimal placental function, substantially increases risks for adverse perinatal and long-term outcomes. The only "treatment" that exists is delivery, which averts stillbirth but does not improve outcomes in survivors. Furthermore, the potential long-term consequences of FGR to the fetus, including cardiometabolic disorders, predispose these individuals to developing FGR in their future pregnancies. This creates a multi-generational cascade of adverse effects stemming from a single dysfunctional placenta, and understanding the mechanisms underlying placental-mediated FGR is critically important if we are to improve outcomes and overall health. The mechanisms behind FGR remain unknown. However, placental insufficiency derived from maldevelopment of the placental vascular systems is the most common etiology. To highlight important mechanistic interactions within the placenta, we focus on placental vascular development in the setting of FGR. We delve into fetoplacental angiogenesis, a robust and ongoing process in normal pregnancies that is impaired in severe FGR. We review cellular models of FGR, with special attention to fetoplacental angiogenesis, and we highlight novel integrin-extracellular matrix interactions that regulate placental angiogenesis in severe FGR. In total, this review focuses on key developmental processes, with specific focus on the human placenta, an underexplored area of research.

Perinatal outcomes of two consecutive strategies for the management of fetal growth restriction: a before-after study

PURPOSE

We aim to compare the perinatal outcomes of two consecutive management strategies for fetal growth restriction (FGR), with or without the inclusion of additional Doppler parameters.

METHODS

A quasi-experimental before/after study was conducted in which we compared a composite perinatal outcome, prematurity rate, and neonatal complications between two management strategies in small fetuses. In the strategy 1 (S1), the management was based on fetal biometry and umbilical artery Doppler. The second strategy (S2) added the assessment of uterine and middle cerebral artery Doppler. We also compared outcomes between strategies according to early (≤ 32 weeks) and late (> 32 weeks) diagnosis subgroups.

RESULTS

We included 396 patients, 163 in S1 and 233 in S2. There were no significant differences in the perinatal composite outcome (p 0.98), prematurity (p 0.19), or in the subgroup analysis. We found a significant reduction in respiratory distress syndrome (RDS) rate with S2 both globally (OR 0.50, p 0.02), and in the early diagnosis subgroup (OR 0.45, p 0.01). In addition, we observed a significant reduction in the incidence of sepsis with S2 both globally (OR 0.30, p 0.04) and in the early diagnosis subgroup (OR 0.25, p 0.02). We did not observe significant differences in necrotizing enterocolitis (p 0.41) and intraventricular hemorrhage (p 1.00).

CONCLUSION

The expanded strategy for the management of FGR did not show significant differences in the primary composite outcome or prematurity. However, it was associated with a lower incidence of RDS and neonatal sepsis.

Impact of Intrauterine Growth Restriction and Placental Insufficiency on Nutritional Outcomes of Extremely Low Birth Weight Infants

Introduction

The aim of our study was to assess the impact of intrauterine growth restriction (IUGR) and placental insufficiency (PI) on the nutritional outcomes of extremely low birth weight (ELBW) infants.

Methods

We conducted a six-year retrospective case-control study that included 117 ELBW infants. Of these, 58 infants had IUGR and 59 were born appropriate-for-gestational age (AGA). Infants with IUGR were further divided based on the presence or absence of PI, as determined by umbilical arterial doppler velocimetry on serial ultrasounds.

Results

IUGR infants with PI had the lowest enteral calorie intake at 28 days of life (DOL) (median intake- IUGR+PI: 32 vs IUGR-PI: 93 vs AGA: 110 kcal/kg/day; p-value 0.011) and at 36 weeks corrected gestational age (CGA) (median intake- IUGR+PI: 102 vs IUGR-PI: 125 vs AGA: 119 kcal/kg/day; p-value 0.012). These infants also trended towards requiring a longer duration of total parenteral nutrition (TPN) (median duration - IUGR+PI: 35 vs IUGR-PI: 25 vs AGA: 21 days; p-value 0.054) and higher incidence of conjugated hyperbilirubinemia (IUGR+PI: 43% IUGR-PI: 29% vs AGA: 16%; p-value 0.058), but these results did not reach statistical significance. Despite challenges with enteral nutrition, IUGR infants with PI showed good catch-up growth and had higher growth velocities over the first month of life, compared to AGA controls.

Conclusion

IUGR in the presence of PI is associated with significantly poorer enteral nutritional outcomes in ELBW infants. However, with the support of optimal parenteral nutrition these infants showed good catch-up growth.

Clinical significance of umbilical artery intermittent versus persistent absent end-diastolic velocity in growth-restricted fetuses

BACKGROUND

Umbilical artery absent end-diastolic velocity (AEDV) indicates increased placental resistance and is associated with increased risk of perinatal demise and neonatal morbidity in fetal growth restriction (FGR). However, the clinical implications of intermittent (iAEDV) versus persistent (pAEDV) absent end-diastolic velocity are unclear.

OBJECTIVE

We compared umbilical artery Doppler (UAD) velocimetry changes during pregnancy and neonatal outcomes in pregnancies with FGR and iAEDV versus pAEDV.

STUDY DESIGN

In this retrospective study of singletons with FGR and AEDV, UAD abnormalities were classified as follows: iAEDV (< 50% cardiac cycles with AEDV) and pAEDV (≥ 50% cardiac cycles AEDV). The primary outcome was UAD progression to reversed end-diastolic velocity (REDV). Secondary outcomes included sustained UAD improvement, latency to delivery, gestational age (GA) at delivery, neonatal morbidity composite, rates of NICU admission, and length of NICU stay. Outcomes were compared between iAEDV and pAEDV. Multivariate logistic regression was used to adjust for confounders. A receiver operative characteristic curve was generated to assess the sensitivity and specificity of the percentage of waveforms with AEDV in predicting the neonatal composite. The Youden's index was used to calculate the optimal cut-point for percentage of waveforms with AEDV to predict the neonatal composite.

RESULTS

Of the 77 patients included, 38 had iAEDV and 39 had pAEDV. Maternal characteristics, including age, parity, and pre-existing conditions did not differ significantly between the two groups. Progression to REDV was less common in iAEDV vs pAEDV (7.9% vs 25.6%, OR 0.25, 95% CI 0.06-0.99). Sustained UAD improvement was more common in iAEDV vs pAEDV (50.0% vs 10.3%; OR 8.75, 95% CI 2.60-29.5). Pregnancies with iAEDV had longer latency to delivery compared to those with pAEDV (11 vs 3 days, p<0.01), and later GA at delivery (33.9 vs 28.7 weeks, p<0.01). Composite neonatal morbidity was less common in the iAEDV group (55.3% vs 92.3%, p<0.01). Neonatal death occurred in 7.9% of iAEDV cases and 33.3% of pAEDV cases (p<0.01). The differences in neonatal outcomes were no longer significant when controlling for GA at delivery. The percentage of cardiac cycles with AEDV is a modest predictor for neonatal morbidity with an AUC of 0.71 (95% CI 0.58-0.84). The optimal cut-point of percent fetal cardiac cycles with AEDV seen at the sentinel ultrasound for predicting neonatal morbidity was calculated to be 47.7%, with a sensitivity of 65% and specificity of 85%.

CONCLUSIONS

Compared to pAEDV, diagnosis of iAEDV in the setting of FGR is associated with lower rates of progression to REDV, higher likelihood of UAD improvement, longer latency to delivery, and later GA at delivery, leading to lower rates of neonatal morbidity and death. Our data support utilizing a cut-point of AEDV in 50% of cardiac cycles to differentiate iAEDV versus pAEDV. This differentiation in growth-restricted fetuses with AEDV may allow further risk stratification.

The role of the fetal biophysical profile in the management of fetal growth restriction

Growth-restricted fetuses are at risk of hypoxemia, acidemia, and stillbirth because of progressive placental dysfunction. Current fetal well-being, neonatal risks following delivery, and the anticipated rate of fetal deterioration are the major management considerations in fetal growth restriction. Surveillance has to quantify the fetal risks accurately to determine the delivery threshold and identify the testing frequency most likely to capture future deterioration and prevent stillbirth. From the second trimester onward, the biophysical profile score correlates over 90% with the current fetal pH, and a normal score predicts a pH >7.25 with a 100% positive predictive value; an abnormal score on the other hand predicts current fetal acidemia with similar certainty. Between 30% and 70% of growth-restricted fetuses with a nonreactive heart rate require biophysical profile scoring to verify fetal well-being, and an abnormal score in 8% to 27% identifies the need for delivery, which is not suspected by Doppler findings. Future fetal well-being is not predicted by the biophysical profile score, which emphasizes the importance of umbilical artery Doppler and amniotic fluid volume to determine surveillance frequency. Studies with integrated surveillance strategies that combine frequent heart rate monitoring with biophysical profile scoring and Doppler report better outcomes and stillbirth rates of between 0% and 4%, compared with those between 8% and 11% with empirically determined surveillance frequency. The variations in clinical behavior and management challenges across gestational age are better addressed when biophysical profile scoring is integrated into the surveillance of fetal growth restriction. This review aims to provide guidance on biophysical profile scoring in the in- and outpatient management of fetal growth restriction.

Human placental villous stromal extracellular matrix regulates fetoplacental angiogenesis in severe fetal growth restriction

Pregnancies complicated by severe, early-onset fetal growth restriction with abnormal Doppler velocimetry (FGRadv) have a sparse villous vascular tree secondary to impaired angiogenesis. As endothelial cell (EC) and stromal matrix interactions are key regulators of angiogenesis, we investigated the role of placental stromal villous matrix on fetoplacental EC angiogenesis. We have developed a novel model of generating placental fibroblast (FB) cell-derived matrices (CDMs), allowing us to interrogate placenta-specific human EC and stromal matrix interactions and their effects on fetoplacental angiogenesis. We found that as compared with control ECs plated on control matrix, FGRadv ECs plated on FGRadv matrix exhibited severe migrational defects, as measured by velocity, directionality, accumulated distance, and Euclidean distance in conjunction with less proliferation. However, control ECs, when interacting with FGRadv CDM, also demonstrated significant impairment in proliferation and migratory properties. Conversely several angiogenic attributes were rescued in FGRadv ECs subjected to control matrix, demonstrating the importance of placental villous stromal matrix and EC-stromal matrix interactions in regulation of fetoplacental angiogenesis.

Fetal Growth Restriction: ACOG Practice Bulletin, Number 227

Fetal growth restriction, also known as intrauterine growth restriction, is a common complication of pregnancy that has been associated with a variety of adverse perinatal outcomes. There is a lack of consensus regarding terminology, etiology, and diagnostic criteria for fetal growth restriction, with uncertainty surrounding the optimal management and timing of delivery for the growth-restricted fetus. An additional challenge is the difficulty in differentiating between the fetus that is constitutionally small and fulfilling its growth potential and the small fetus that is not fulfilling its growth potential because of an underlying pathologic condition. The purpose of this document is to review the topic of fetal growth restriction with a focus on terminology, etiology, diagnostic and surveillance tools, and guidance for management and timing of delivery.

Intrapartum Doppler ultrasound: where are we now?

Intrapartum hypoxic events most commonly occur in low-risk pregnancies with appropriately grown fetuses. Continuous intrapartum monitoring by means of cardiotocography has not demonstrated a reduction in the frequency of adverse perinatal outcome but has been linked with an increase in the caesarean section rate, particularly among women considered at low risk. Available data from the literature suggests that abnormalities in the uterine artery Doppler and in the ratio between fetal cerebral and umbilical Doppler (i.e. cerebroplacental ratio [CPR]) are associated with conditions of subclinical placental function occurring in fetuses who have failed to achieve their growth potential regardless of their actual size. In this review we summarize the available evidence on the use of intrapartum Doppler ultrasound for the fetal surveillance during labor and the identification of the fetuses at risk of intrapartum distress.

Sonographic Assessment of Fetal Growth Abnormalities

Fetal growth abnormalities have significant consequences for pregnancy management and maternal and fetal well-being. The accurate diagnosis of fetal growth abnormalities contributes to optimal antenatal management, which may minimize the sequelae of inadequate or excessive fetal growth. An accurate diagnosis of abnormal fetal growth depends on accurate pregnancy dating and serial growth measurements. The fetal size at any given stage of pregnancy is either appropriate or inappropriate for the given gestational age (GA). Pregnancy dating is most accurate in the first trimester, as biologic variability does not come into play until the second and third trimesters. The authors describe the determination of GA with use of standard US measurements and how additional parameters can be used to confirm dating. Once dates are established, serial measurements are used to identity abnormal growth patterns. The sometimes confusing definitions of abnormal growth are clarified, the differentiation of a constitutionally small but healthy fetus from a growth-restricted at-risk fetus is described, and the roles of Doppler US and other adjunctive examinations in the management of growth restriction are discussed. In addition, the definition of selective growth restriction in twin pregnancy is briefly discussed, as is the role of Doppler US in the classification of subtypes of selective growth restriction in monochorionic twinning. The criteria for diagnosing macrosomia and the management of affected pregnancies also are reviewed. The importance of correct pregnancy dating in the detection and surveillance of abnormal fetal growth and for prevention of perinatal maternal and fetal morbidity and mortality cannot be overstated. The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2020.

Do Doppler Changes Reflect Pathology of Placental Vascular Lesions in IUGR Pregnancies?

OBJECTIVES

Doppler assessment of uteroplacental (UP) and fetoplacental (FP) circulation detects abnormal waveforms in intrauterine growth-restricted (IUGR) pregnancies. Similarly, histopathology also reveals lesions of vascular compromise in IUGR placenta. We evaluated an association between Doppler and histopathological (HP) assessment of the maternal and fetal circulation in IUGR.

METHODS

IUGR cases with both Doppler and histopathology assessment were selected from our database. Doppler patterns recorded UP and FP insufficiency. The HP vascular lesions were classified as maternal vascular underperfusion and fetal thrombotic vasculopathy (FTV). IUGRs were grouped based on (i) presence of preeclampsia (PE), (ii) clinical onset (early vs late) of IUGR (early onset [EO]/late onset), and (iii) gestational age (term, T/preterm, PT).

RESULTS

Abnormal Doppler waveforms were present in 69 of the total 88 IUGR cases (78.4%). The most frequent pattern was fetoplacental insufficiency (FPI) (66%) which was combined with uteroplacental insufficiency (UPI) in 49%. HP showed vascular lesions in 52.3% and most frequent was FTV (38%). PE-associated IUGR (n = 49) had higher UPI pattern (75.5% vs 43.6%, P = .004), while normotensive IUGR had higher FPI pattern (28.2% vs 8.2%, P = .01). EO-IUGR (n = 55) and PT-IUGR (n = 52) had significant abnormal Doppler waveforms (P < .05) with higher combined patterns and brain sparing. Doppler was more sensitive for fetal vascular lesions than maternal (75.8% vs 66.7%). However, 42% of cases with normal Doppler findings showed HP vascular lesions.

CONCLUSION

IUGR pregnancies harbor significant vascular compromise. Fetal circulatory lesions were more common in IUGR pregnancies. In a significant number of cases with normal Doppler report, vascular lesions were identified on histopathology, emphasizing placental examination in all cases of IUGR.

No. 197a-Fetal Health Surveillance: Antepartum Consensus Guideline

OBJECTIVE

This guideline provides new recommendations pertaining to the application and documentation of fetal surveillance in the antepartum period that will decrease the incidence of birth asphyxia while maintaining the lowest possible rate of obstetrical intervention. Pregnancies with and without risk factors for adverse perinatal outcomes are considered. This guideline presents an alternative classification system for antenatal fetal non-stress testing to what has been used previously. This guideline is intended for use by all health professionals who provide antepartum care in Canada.

OPTIONS

Consideration has been given to all methods of fetal surveillance currently available in Canada.

OUTCOMES

Short- and long-term outcomes that may indicate the presence of birth asphyxia were considered. The associated rates of operative and other labour interventions were also considered.

EVIDENCE

A comprehensive review of randomized controlled trials published between January 1996 and March 2007 was undertaken, and MEDLINE and the Cochrane Database were used to search the literature for all new studies on fetal surveillance antepartum. The level of evidence has been determined using the criteria and classifications of the Canadian Task Force on Preventive Health Care (Table 1).

SPONSOR

This consensus guideline was jointly developed by the Society of Obstetricians and Gynaecologists of Canada and the British Columbia Perinatal Health Program (formerly the British Columbia Reproductive Care Program or BCRCP) and was partly supported by an unrestricted educational grant from the British Columbia Perinatal Health Program. RECOMMENDATION 1: FETAL MOVEMENT COUNTING: RECOMMENDATION 2: NON-STRESS TEST: RECOMMENDATION 3: CONTRACTION STRESS TEST: RECOMMENDATION 4: BIOPHYSICAL PROFILE: RECOMMENDATION 5: UTERINE ARTERY DOPPLER: RECOMMENDATION 6: UMBILICAL ARTERY DOPPLER.

Overexpression of the aryl hydrocarbon receptor nuclear translocator partially rescues fetoplacental angiogenesis in severe fetal growth restriction

Pregnancies complicated by severe fetal growth restriction with abnormal umbilical artery Doppler velocimetry (FGRadv) are at substantial risk for adverse perinatal and long-term outcomes. Impaired angiogenesis of the placental vasculature in these pregnancies results in a sparse, poorly branched vascular tree, which structurally contributes to the abnormally elevated fetoplacental vascular resistance that is clinically manifested by absent or reversed umbilical artery Doppler indices. Previous studies have shown that aryl hydrocarbon receptor nuclear translocator (ARNT) is a key mediator of proper placental angiogenesis, and within placental endothelial cells (ECs) from human FGRadv pregnancies, low expression of ARNT leads to decreased vascular endothelial growth factor A (VEGFA) expression and deficient tube formation. Thus, the aim of the present study was to determine the effect of VEGFA administration or ARNT overexpression on angiogenic potential of FGRadv ECs. ECs were isolated and cultured from FGRadv or gestational age-matched control placentas and subjected to either vehicle vs VEGFA treatment or transduction with adenoviral-CMV (ad-CMV) vs adenoviral-ARNT (ad-ARNT) constructs. They were then assessed via wound scratch and tube formation assays. We found that VEGFA administration nominally improved FGRadv EC migration (P<0.01) and tube formation (P<0.05). ARNT overexpression led to significantly enhanced ARNT expression in FGRadv ECs (P<0.01), to a level similar to control ECs. Despite this, FGRadv EC migration (P<0.05) and tube formation (P<0.05) were still only partially rescued. This suggests that although ARNT does play a role in fetoplacental EC migration, other factors in addition to ARNT are likely also important in placental angiogenesis.

Antenatal placental assessment in the prediction of adverse pregnancy outcome after reduced fetal movement

OBJECTIVE

To assess the value of in utero placental assessment in predicting adverse pregnancy outcome after reported reduced fetal movements (RFM).

METHOD

A non-interventional prospective cohort study of women (N = 300) with subjective RFM at ≥28 weeks' gestation in singleton non-anomalous pregnancies at a UK tertiary maternity hospital. Clinical, sonographic (fetal weight, placental size and maternal, fetal and placental arterial Doppler) and biochemical (maternal serum hCG, hPL, progesterone, PlGF and sFlt-1) assessment was conducted. Multiple logistic regression identified combinations of measurements (models) most predictive of adverse pregnancy outcome (perinatal mortality, birth weight <10th centile, five minute Apgar score <7, umbilical arterial pH <7.1 or base excess <-10, neonatal intensive care admission). Models were compared by test performance characteristics (ROC curve, sensitivity, specificity, positive/negative predictive value, positive/negative likelihood ratios) against baseline care (estimated fetal weight centile, amniotic fluid index and gestation at presentation).

RESULTS

61 (20.6%) pregnancies ended in adverse outcome. Models incorporating PlGF/sFlt-1 ratio and umbilical artery free loop Doppler impedance demonstrated modest improvement in ROC area for adverse outcome (baseline care 0.69 vs. proposed models 0.73-0.76, p<0.05). However, there was little improvement in other test characteristics (baseline vs. best proposed model: sensitivity 21.7% [95% confidence interval 13.1-33.6] vs. 35.8%% [24.4-49.3], specificity 96.6% [93.4-98.3] vs. 94.7% [90.7-97.0], PPV 61.9% [40.9-79.3] vs. 63.3% [45.5-78.1], NPV 82.8% [77.9-86.8] vs. 85.2% [80.0-89.2], positive LR 6.3 [2.8-14.6] vs. 6.7 [3.4-3.3], negative LR 0.81 [0.71-0.93] vs. 0.68 [0.55-0.83]) and wide confidence intervals. Negative post-test probability remained high (16.7% vs. 14.0%).

CONCLUSION

Antenatal placental assessment may improve identification of RFM pregnancies at highest risk of adverse pregnancy outcome but further work is required to understand and refine currently available outcome definitions and diagnostic techniques to improve clinical utility.

Managing fetal growth restriction: surveillance tests and their interpretation

The main challenges in pregnancies affected by fetal growth restriction consist in identifying signs of disease progression and determining the appropriate timing of delivery. The risk of continuing the pregnancy must be balanced with the risk of prematurity, which depends on gestational age. To allow appropriate monitoring of the growth-restricted fetus, several surveillance tests are available. These include ultrasound Doppler velocimetry of feto-placental vessels, cardiotocography, and amniotic fluid evaluation. It is well known that the combination of tests performs better than each test alone to predict fetal deterioration. The interpretation of test results depends on the gestational age and on the nature of the growth disorder (early- vs. late-onset disease). Appropriate knowledge on the surveillance tests interpretation and the frequency at which they need to be performed is crucial in managing fetal growth restriction, in order to produce better outcome and prevent stillbirth, and at the same time to avoid unnecessary interventions.

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.

Intrauterine Growth Restriction. Guideline of the German Society of Gynecology and Obstetrics (S2k-Level, AWMF Registry No. 015/080, October 2016)

AIMS

The aim of this official guideline published and coordinated by the German Society of Gynecology and Obstetrics (DGGG) was to provide consensus-based recommendations obtained by evaluating the relevant literature for the diagnostic treatment and management of women with fetal growth restriction.

METHODS

This S2k guideline represents the structured consensus of a representative panel of experts with a range of different professional backgrounds commissioned by the Guideline Committee of the DGGG.

RECOMMENDATIONS

Recommendations for diagnostic treatment, management, counselling, prophylaxis and screening are presented.

Gestational Protein Restriction Increases Cardiac Connexin 43 mRNA levels in male adult rat offspring

Background

The dietary limitation during pregnancy influences the growth and development of the fetus and offspring and their health into adult life. The mechanisms underlying the adverse effects of gestational protein restriction (GPR) in the development of the offspring hearts are not well understood.

Objectives

The aim of this study was to evaluate the effects of GPR on cardiac structure in male rat offspring at day 60 after birth (d60).

Methods

Pregnant Wistar rats were fed a normal-protein (NP, 17% casein) or low-protein (LP, 6% casein) diet. Blood pressure (BP) values from 60-day-old male offspring were measured by an indirect tail-cuff method using an electro sphygmomanometer. Hearts (d60) were collected for assessment of connexin 43 (Cx43) mRNA expression and morphological and morphometric analysis.

Results

LP offspring showed no difference in body weight, although they were born lighter than NP offspring. BP levels were significantly higher in the LP group. We observed a significant increase in the area occupied by collagen fibers, a decrease in the number of cardiomyocytes by 10⁴µm², and an increase in cardiomyocyte area associated with an increased Cx43 expression.

Conclusion

GPR changes myocardial levels of Cx43 mRNA in male young adult rats, suggesting that this mechanism aims to compensate the fibrotic process by the accumulation of collagen fibers in the heart interstitium.

Hematological changes in severe early onset growth-restricted fetuses with absent and reversed end-diastolic flow in the umbilical artery

BACKGROUND

Erythropoietin seems to play an important role in the regulation of fetal hypoxemia. The present prospective study was designed to determine if changes in erythropoietin levels can be found in fetuses with severe early-onset growth restriction and hemodynamic compromise.

METHODS AND RESULTS

Erythropoietin, hemoglobin, hematocrit, platelet counts, normoblasts, lacate, arterial and venous blood gasses in the umbilical cord were determined in 42 fetuses with fetal growth restriction (IUGR) with absent (zero-flow) and 26 IUGR fetuses with retrograde end-diastolic flow (reverse-flow) in the umbilical artery. Color Doppler measurements were performed on the middle cerebral artery (PI) and ductus venosus [(S-a)/D and (S-a)/Vmean]. Erythropoietin concentrations were significantly lower in the zero-flow group (median: 128.0 mU/mL; range: 60.3-213 mU/mL) compared with the reverse-flow group (median: 202.5 mU/mL; range: 166-1182 mU/mL). Significant differences in median lactate concentrations were observed between the zero-flow group: 3.28 mmol/L (range; 2.3-4.7 mmol/L), and reverse-flow group: 5.6 mmol/L (range: 3.8-7.5 mmol/L). Fetuses with reverse-flow had significantly lower median platelet counts than fetuses with zero-flow (74 vs. 155/μL) and significantly lower normoblast counts (63 vs. 342/100 WBC).

CONCLUSIONS

Fetuses with severe IUGR due to chronic placental insufficiency and absent or reversed flow in the umbilical artery show increased erythropoietin levels.

Dietary interventions for fetal growth restriction - therapeutic potential of dietary nitrate supplementation in pregnancy

Fetal growth restriction (FGR) affects around 5% of pregnancies and is associated with significant short- and long-term adverse outcomes. A number of factors can increase the risk of FGR, one of which is poor maternal diet. In terms of pathology, both clinically and in many experimental models of FGR, impaired uteroplacental vascular function is implicated, leading to a reduction in the delivery of oxygen and nutrients to the developing fetus. Whilst mechanisms underpinning impaired uteroplacental vascular function are not fully understood, interventions aimed at enhancing nitric oxide (NO) bioavailability remain a key area of interest in obstetric research. In addition to endogenous NO production from the amino acid l-arginine, via nitric oxide synthase (NOS) enzymes, research in recent years has established that significant NO can be derived from dietary nitrate, via the 'alternative NO pathway'. Dietary nitrate, abundant in green leafy vegetables and beetroot, can increase NO bioactivity, conferring beneficial effects on cardiovascular function and blood flow. Given the beneficial effects of dietary nitrate supplementation to date in non-pregnant humans and animals, current investigations aim to assess the therapeutic potential of this approach in pregnancy to enhance NO bioactivity, improve uteroplacental vascular function and increase fetal growth.

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.

Correlation between Doppler flow patterns in growth-restricted fetuses and neonatal circulation

OBJECTIVES

To investigate whether prenatal Doppler parameters in growth-restricted fetuses are correlated with neonatal circulatory changes.

METHODS

In 43 cases of suspected fetal growth restriction (FGR), serial Doppler measurements of umbilical artery (UA) and middle cerebral artery (MCA) pulsatility index (PI) were performed. The last measurement, closest to delivery (< 1 week before birth), was used for analysis. Neonatal circulation was assessed for 2 h/day on Days 1-5, 8 and 15 by near-infrared spectroscopy (NIRS) of the cerebral, renal and splanchnic regions. We calculated fractional tissue oxygen extraction (FTOE) as: (arterial oxygen saturation - NIRS value)/arterial oxygen saturation. The following ratios were calculated: cerebroplacental ratio (CPR; MCA-PI/UA-PI), cerebrorenal ratio (CRR; cerebral/renal FTOE) and cerebrosplanchnic ratio (CSR; cerebral/splanchnic FTOE). Spearman's rank correlation coefficient (ρ) was calculated between prenatal Doppler parameters and neonatal NIRS variables. These analyses were carried out for the entire group, and separately for cases of early FGR (delivered < 34 weeks) and late FGR (≥ 34 weeks).

RESULTS

Fetal Doppler parameters correlated with neonatal NIRS variables on Days 1-3: UA-PI correlated with renal FTOE (Day 1: ρ = 0.454, P < 0.01) and CRR (Day 1: ρ = -0.517, P < 0.001). MCA-PI correlated with cerebral FTOE on Day 2 (ρ = 0.469, P < 0.01), approached statistical significance on Day 3 but was not correlated on Day 1. CPR correlated with CRR (Day 1: ρ = 0.474, P < 0.01). Most associations lost their statistical significance when early and late FGR subgroups were considered separately.

CONCLUSION

Low MCA-PI and low CPR, indicating brain sparing before birth, are associated with low CRR after birth, indicating relatively greater blood flow to the cerebrum than to the renal region. Based on the results of this study, it could be speculated that if brain sparing is present in the fetal circulation, it persists during the first 3 days after birth. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Novel treatment strategies for smooth muscle disorders: Targeting Kv7 potassium channels

Smooth muscle cells provide crucial contractile functions in visceral, vascular, and lung tissues. The contractile state of smooth muscle is largely determined by their electrical excitability, which is in turn influenced by the activity of potassium channels. The activity of potassium channels sustains smooth muscle cell membrane hyperpolarization, reducing cellular excitability and thereby promoting smooth muscle relaxation. Research over the past decade has indicated an important role for Kv7 (KCNQ) voltage-gated potassium channels in the regulation of the excitability of smooth muscle cells. Expression of multiple Kv7 channel subtypes has been demonstrated in smooth muscle cells from viscera (gastrointestinal, bladder, myometrial), from the systemic and pulmonary vasculature, and from the airways of the lung, from multiple species, including humans. A number of clinically used drugs, some of which were developed to target Kv7 channels in other tissues, have been found to exert robust effects on smooth muscle Kv7 channels. Functional studies have indicated that Kv7 channel activators and inhibitors have the ability to relax and contact smooth muscle preparations, respectively, suggesting a wide range of novel applications for the pharmacological tool set. This review summarizes recent findings regarding the physiological functions of Kv7 channels in smooth muscle, and highlights potential therapeutic applications based on pharmacological targeting of smooth muscle Kv7 channels throughout the body.

Tumor-homing peptides as tools for targeted delivery of payloads to the placenta

The availability of therapeutics to treat pregnancy complications is severely lacking mainly because of the risk of causing harm to the fetus. As enhancement of placental growth and function can alleviate maternal symptoms and improve fetal growth in animal models, we have developed a method for targeted delivery of payloads to the placenta. We show that the tumor-homing peptide sequences CGKRK and iRGD bind selectively to the placental surface of humans and mice and do not interfere with normal development. Peptide-coated nanoparticles intravenously injected into pregnant mice accumulated within the mouse placenta, whereas control nanoparticles exhibited reduced binding and/or fetal transfer. We used targeted liposomes to efficiently deliver cargoes of carboxyfluorescein and insulin-like growth factor 2 to the mouse placenta; the latter significantly increased mean placental weight when administered to healthy animals and significantly improved fetal weight distribution in a well-characterized model of fetal growth restriction. These data provide proof of principle for targeted delivery of drugs to the placenta and provide a novel platform for the development of placenta-specific therapeutics.

The impact of fetal growth restriction on latency in the setting of expectant management of preeclampsia

BACKGROUND

Fetal growth restriction is a common complication of preeclampsia. Expectant management for qualifying patients has been found to have acceptable maternal safety while improving neonatal outcomes. Whether fetal growth restriction influences the duration of latency during expectant management of preeclampsia is unknown.

OBJECTIVE

The objective of the study was to determine whether fetal growth restriction is associated with a reduced interval to delivery in women with preeclampsia being expectantly managed prior to 34 weeks.

STUDY DESIGN

We performed a retrospective cohort of singleton, live-born, nonanomalous deliveries at the University of Cincinnati Medical Center between 2008 and 2013. Patients were included in our analysis if they were diagnosed with preeclampsia prior to 34 completed weeks and if the initial management plan was to pursue expectant management beyond administration of steroids for fetal lung maturity. Two study groups were determined based on the presence or absence of fetal growth restriction. Patients were delivered when they developed persistent neurological symptoms, severe hypertension refractory to medical therapy, renal insufficiency, nonreassuring fetal status, pulmonary edema, or hemolysis elevated liver low platelet syndrome or when they reached 37 weeks if they remained stable without any other indication for delivery. Our primary outcome was the interval from diagnosis of preeclampsia to delivery, measured in days. Secondary outcomes included indications for delivery, rates of induction and cesarean delivery, development of severe morbidities of preeclampsia, and select neonatal outcomes. We performed a multivariate logistic regression analysis comparing those with fetal growth restriction with those with normally grown fetuses to determine whether there is an association between fetal growth restriction and a shortened interval to delivery, neonatal intensive care unit admission, prolonged neonatal stay, and neonatal mortality.

RESULTS

A total of 851 patients met the criteria for preeclampsia, of which 199 met inclusion criteria, 139 (69%) with normal growth, and 60 (31%) with fetal growth restriction. Interval to delivery was significantly shorter in women with fetal growth restriction, median (interquartile range) of 3 (1.6) days vs normal growth, 5 (2.12) days, P < .001. The association between fetal growth restriction and latency less than 7 days remained significant, even after post hoc analysis controlling for confounding variables (adjusted odds ratio, 1.66 [95% confidence interval, 1.12-2.47]). There were no differences in the development of severe disease (85.9 vs 91.7%, P = .26), need for intravenous antihypertensive medications (47.1 vs 46.7%, P = .96), and the development of severe complications of preeclampsia (51.1 vs 42.9%, P = .30) in normally grown and growth-restricted fetuses, respectively. Fewer women with fetal growth restriction attained their scheduled delivery date, 3 of 60 (5.0%), compared with normally grown fetuses,12 of 139 (15.7%), P = .03. Admission to the neonatal intensive care unit, neonatal length of stay, and neonatal mortality were higher when there was fetal growth restriction; however, after a logistic regression analysis, these associations were no longer significant.

CONCLUSION

Fetal growth restriction is associated with a shortened interval to delivery in women undergoing expectant management of preeclampsia when disease is diagnosed prior to 34 weeks. These data may be helpful in counseling patients regarding the expected duration of pregnancy, guiding decision making regarding administration of steroids and determining the need for maternal transport.

Antenatal tests of fetal wellbeing

In current obstetric practice, there is frequently a need to assess fetal wellbeing. This is particularly so in those fetuses at risk, including the small-for-gestational-age fetus or the fetus of a mother who presents with reduced fetal movements or who has an obstetric complication such as pre-eclampsia. It is important that the clinician is able to assess fetal wellbeing in such cases, especially in preterm gestations, when inappropriate delivery could have serious adverse consequences. In this paper, we review the current evidence for the use and the limitations of widely used methods of antenatal monitoring including the use of cardiotocography, biophysical profile, and ultrasound-derived parameters including umbilical artery, middle cerebral artery, and ductus venosus Doppler flow.

Multiscale modelling of the feto-placental vasculature

The placenta provides all the nutrients required for the fetus through pregnancy. It develops dynamically, and, to avoid rejection of the fetus, there is no mixing of fetal and maternal blood; rather, the branched placental villi 'bathe' in blood supplied from the uterine arteries. Within the villi, the feto-placental vasculature also develops a complex branching structure in order to maximize exchange between the placental and maternal circulations. To understand the development of the placenta, we must translate functional information across spatial scales including the interaction between macro- and micro-scale haemodynamics and account for the effects of a dynamically and rapidly changing structure through the time course of pregnancy. Here, we present steps towards an anatomically based and multiscale approach to modelling the feto-placental circulation. We assess the effect of the location of cord insertion on feto-placental blood flow resistance and flow heterogeneity and show that, although cord insertion does not appear to directly influence feto-placental resistance, the heterogeneity of flow in the placenta is predicted to increase from a 19.4% coefficient of variation with central cord insertion to 23.3% when the cord is inserted 2 cm from the edge of the placenta. Model geometries with spheroidal and ellipsoidal shapes, but the same volume, showed no significant differences in flow resistance or heterogeneity, implying that normal asymmetry in shape does not affect placental efficiency. However, the size and number of small capillary vessels is predicted to have a large effect on feto-placental resistance and flow heterogeneity. Using this new model as an example, we highlight the importance of taking an integrated multi-disciplinary and multiscale approach to understand development of the placenta.

Activation of KV7 channels stimulates vasodilatation of human placental chorionic plate arteries

INTRODUCTION

Potassium (K(+)) channels are key regulators of vascular smooth muscle cell (VSMC) excitability. In systemic small arteries, Kv7 channel expression/activity has been noted and a role in vascular tone regulation demonstrated. We aimed to demonstrate functional Kv7 channels in human fetoplacental small arteries.

METHODS

Human placental chorionic plate arteries (CPAs) were obtained at term. CPA responses to Kv7 channel modulators was determined by wire myography. Presence of Kv7 channel mRNA (encoded by KCNQ1-5) and protein expression were assessed by RT-PCR and immunohistochemistry/immunofluorescence, respectively.

RESULTS

Kv7 channel blockade with linopirdine increased CPA basal tone and AVP-induced contraction. Pre-contracted CPAs (AVP; 80 mM K(+) depolarization solution) exhibited significant relaxation to flupirtine, retigabine, the acrylamide (S)-1, and (S) BMS-204352, differential activators of Kv7.1 - Kv7.5 channels. All CPAs assessed expressed KCNQ1 and KCNQ3-5 mRNA; KCNQ2 was expressed only in a subset of CPAs. Kv7 protein expression was confirmed in intact CPAs and isolated VSMCs.

DISCUSSION

Kv7 channels are present and active in fetoplacental vessels, contributing to vascular tone regulation in normal pregnancy. Targeting these channels may represent a therapeutic intervention in pregnancies complicated by increased vascular resistance.

Impaired fetoplacental angiogenesis in growth-restricted fetuses with abnormal umbilical artery doppler velocimetry is mediated by aryl hydrocarbon receptor nuclear translocator (ARNT)

CONTEXT

Fetal growth restriction with abnormal umbilical artery Doppler velocimetry (FGRadv), reflective of elevated fetoplacental vascular resistance, is associated with increased risks of fetal morbidity and mortality even in comparison to those of growth-restricted fetuses with normal placental blood flow. One major cause of this abnormally elevated fetoplacental vascular resistance is the aberrantly formed, thin, elongated villous vessels that are seen in FGRadv placentas.

OBJECTIVE

The purpose of this study was to determine the role of fetoplacental endothelial cells (ECs) in angiogenesis in normal pregnancies and in those complicated by FGRadv.

DESIGN AND PARTICIPANTS

Human placental specimens were obtained from FGRadv and gestational age-matched, appropriately grown control pregnancies for EC isolation/culture and for immunohistochemical studies. Additional mechanistic studies were performed on ECs isolated from subjects with term, uncomplicated pregnancies.

MAIN OUTCOME MEASURES

We evaluated tube formation and differential angiogenic gene expression in FGRadv and control ECs, and we used ECs from uncomplicated pregnancies to further elucidate the molecular mechanisms by which angiogenesis is impaired in FGRadv pregnancies.

RESULTS

Tube formation assays showed that FGRadv ECs demonstrate fewer branch points and total length compared with those from gestational age-matched controls, and this defect was not rescued by exposure to hypoxia. FGRadv ECs also demonstrated lower aryl hydrocarbon receptor nuclear translocator (ARNT) expression. ARNT knockdown resulted in suppression of key angiogenic genes including vascular endothelial growth factor A expression and led to deficient tube formation.

CONCLUSIONS

ARNT expression in the placental vasculature mediates key angiogenic expression and fetoplacental EC angiogenesis, and low ARNT expression in FGRadv ECs appears to be a key factor in deficient angiogenesis. This, in turn, results in malformed thin villous vessels that structurally contribute to the abnormally elevated fetoplacental vascular resistance that is associated with high morbidity and mortality in fetal growth restriction.

Three-dimensional placental volume and mean grey value: Normal ranges in a Turkish population and correlation with maternal serum biochemistry and Doppler parameters

The aim of this study is to evaluate the relationship between three-dimensional (3D) ultrasound measurements of placenta at 11-13(6) weeks' gestation and maternal serum levels of pregnancy associated plasma protein-A (PAPP-A), free beta human chorionic gonadotrophin (fβhCG), Doppler parameters in early pregnancy. This prospective study consisted of 334 singleton pregnancies at 11-13(6) weeks' gestation. Placental volume and placental volumetric mean grey values were evaluated. The placental volume (cm(3)) was analysed using the Virtual Organ Computer-aided AnaLysis (VOCAL) imaging program and 3D histogram was used to calculate the volumetric mean grey value (%). Mean maternal age was 28.35 ± 7.55. Mean gestational age was 12.29 ± 0.68 weeks. Placental volume was 77.04 ± 35.74 cm(3). Mean grey value of the placenta was 34.38 ± 8.02%. Correlation analysis revealed that placental volume was significantly correlated with the crown-rump length (r = 0.173, p = 0.002), gestational week (r = 0.116, p = 0.036), ductus venosus pulsatility index (r = -0.101, p = 0.04) and maternal weight (r = 0.099, p = 0.037). There was a significant relation between the mean grey value of the placenta and maternal age (r = 0.131, p = 0.02), nuchal translucency (r = -0.109, p = 0.048), PAPP-A (r = 0.108, p = 0.04) and fβhCG (r = 0.104, p = 0.042). Volumetry of the placenta can be carried out with a high percentage of 1st trimester pregnancies. Volumetry during the 1st trimester could be helpful because of the less advanced state of placentation. This examination is easy to perform and the measurements can be acquired correctly and quickly.

First-trimester prediction of small-for-gestational age neonates incorporating fetal Doppler parameters and maternal characteristics

OBJECTIVE

First-trimester screening for subsequent delivery of a small-for-gestational-age (SGA) infant typically focuses on maternal risk factors and uterine artery (UtA) Doppler. Our aim is to test if incorporation of fetal umbilical artery (UA) and ductus venosus (DV) Doppler improves SGA prediction.

STUDY DESIGN

Prospective screening study of singletons at 11-14 weeks. Maternal characteristics, serum concentrations of pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin are ascertained and UtA Doppler, UA, and DV Doppler studies are performed. These parameters are tested for their ability to predict subsequent delivery of a SGA infant.

RESULTS

Among 2267 enrolled women, 191 (8.4%) deliver an SGA infant. At univariate analysis women with SGA neonates are younger, more frequently African-American (AA), nulliparous, more likely to smoke, have lower PAPP-A and free β-human chorionic gonadotropin levels. They have a higher incidence of UtA Doppler bilateral notching, higher mean UtA Doppler-pulsatility index z-scores (P < .001) and UA pulsatility index z-scores (P = .03), but no significant difference in DV-pulsatility index z-scores or in the incidence of abnormal qualitative UA and DV patterns. Multivariate logistic regression analysis identifies nulliparity and AA ethnicity (P < .001), PAPP-A multiple of the median and bilateral notching (P < .05) as determinants of SGA infant. Predictive sensitivity was low; receiver operating characteristic curve analysis yields areas under the curve of 0.592 (95% confidence interval, 0.548-0.635) for the combination of UtA Doppler and UA pulsatility index z-scores.

CONCLUSION

Delivery of a SGA infant is most frequent in nulliparous women of AA ethnicity. Despite the statistical association with UtA Doppler first-trimester SGA prediction is poor and not improved by the incorporation of fetal Doppler.

Two-year neurological outcome of very-low-birth-weight children with prenatal absent or reversed end-diastolic flow velocity in the umbilical artery

OBJECTIVE

The aim of this study was to investigate the 2-year neurological outcome of very-low-birth-weight (VLBW) children who had abnormal umbilical blood flow velocity prenatally.

MATERIALS AND METHODS

We performed a prospective collection of infants prenatally diagnosed with abnormal umbilical blood flow velocity at a tertiary referral center from January 1, 2001 to September 30, 2005. VLBW children with prenatal absent or reversed end-diastolic flow velocity (AREDV) in the umbilical artery were investigated and compared with two similar demographic control groups of VLBW children without AREDV: one group with fetal growth restriction and the other without it. A follow-up study at 2 years of age for Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI) of the Bayley Scales among the three groups was analyzed.

RESULTS

Twenty-four VLBW children were identified to have AREDV prenatally, of whom four died during the neonatal period. After 2 years, five children were lost to follow-up and 15 were rescued, of whom 11 had absent end-diastolic velocity and four reversed end-diastolic velocity. We compared the remaining 15 children with the two control groups [28 children in the matched control group with intrauterine fetal growth restriction (IUGR), and 38 children in the matched control group without IUGR], and no significant differences were found in MDI (p = 0.938) and PDI (p = 0.496) scores at 2 years of age. However, we also surveyed the children with a gestational age of ≤ 29 weeks and found a significant difference in MDI scores (p = 0.048), but not in PDI scores (p = 0.219), among the three groups.

CONCLUSION

VLBW children delivered earlier than 29 gestational weeks with abnormal umbilical blood flow velocity prenatally have greater mental developmental delay at 2 years of age.

Postnatal systemic blood flow in neonates with abnormal fetal umbilical artery Doppler

Objective. Abnormal umbilical artery Doppler (UAD) studies are associated with poor neonatal outcomes. We sought to determine if postnatal measures of systemic blood flow (SBF), as measured by functional echocardiography (fECHO), could identify which fetuses with abnormal UAD were at the highest risk of adverse outcomes. Study Design. This is a retrospective review of fetuses with abnormal UAD who received fECHO in the first 72 hours of life. Measures of SBF (right ventricular output (RVO) and superior vena cava (SVC) flow) were performed and compared with prenatal variables and postnatal outcomes. Result. 63 subjects had abnormal UAD, 20 of which also had fECHO. Six subjects had abnormal flow. Gestational age at delivery was similar between the two groups. Those with abnormal SBF had fewer days of abnormal UAD prior to delivery and developed RDS (P < 0.001). Conclusion. Postnatal measures of SBF were associated with poor postnatal outcomes in fetuses with abnormal UAD. Future studies incorporating antenatal measures of SBF may help obstetricians determine which pregnancies complicated by UAD are likely to have postnatal morbidity.

Risk of necrotizing enterocolitis and feeding interventions for preterm infants with abnormal umbilical artery Doppler

Infants exposed to absent or reversed end-diastolic flow (ARE DF) in utero may be at an increased risk of developing necrotizing enterocolitis (NEC). This article reviews placental function and the development of ARE DF. Studies examining the relationship between AREDF and NEC are reviewed, yet research remains inconclusive regarding this relationship. Recent studies reveal that early minimal enteral feeding does not increase the incidence of NEC in infants with AREDF. Initiation and advancement of enteral feedings should be monitored closely in this subset of the neonatal intensive care unit (NICU) population.

Fetal echocardiography and pulsed-wave Doppler ultrasound in a rabbit model of intrauterine growth restriction

Fetal intrauterine growth restriction (IUGR) results in abnormal cardiac function that is apparent antenatally due to advances in fetoplacental Doppler ultrasound and fetal echocardiography. Increasingly, these imaging modalities are being employed clinically to examine cardiac function and assess wellbeing in utero, thereby guiding timing of birth decisions. Here, we used a rabbit model of IUGR that allows analysis of cardiac function in a clinically relevant way. Using isoflurane induced anesthesia, IUGR is surgically created at gestational age day 25 by performing a laparotomy, exposing the bicornuate uterus and then ligating 40-50% of uteroplacental vessels supplying each gestational sac in a single uterine horn. The other horn in the rabbit bicornuate uterus serves as internal control fetuses. Then, after recovery at gestational age day 30 (full term), the same rabbit undergoes examination of fetal cardiac function. Anesthesia is induced with ketamine and xylazine intramuscularly, then maintained by a continuous intravenous infusion of ketamine and xylazine to minimize iatrogenic effects on fetal cardiac function. A repeat laparotomy is performed to expose each gestational sac and a microultrasound examination (VisualSonics VEVO 2100) of fetal cardiac function is performed. Placental insufficiency is evident by a raised pulsatility index or an absent or reversed end diastolic flow of the umbilical artery Doppler waveform. The ductus venosus and middle cerebral artery Doppler is then examined. Fetal echocardiography is performed by recording B mode, M mode and flow velocity waveforms in lateral and apical views. Offline calculations determine standard M-mode cardiac variables, tricuspid and mitral annular plane systolic excursion, speckle tracking and strain analysis, modified myocardial performance index and vascular flow velocity waveforms of interest. This small animal model of IUGR therefore affords examination of in utero cardiac function that is consistent with current clinical practice and is therefore useful in a translational research setting.

The role of apoptosis on trophoblast cell invasion in the placental bed of normotensive and preeclamptic pregnancies

BACKGROUND

Placental development depends on careful coordination of trophoblast proliferation and apoptosis; however, the synchrony of its effect on trophoblast invasion is unknown.

OBJECTIVE

To examine the relationship between trophoblast apoptosis and proliferation in placental bed tissue of preeclamptic and normotensive pregnancies.

METHODS

Serial sections from archived placental bed biopsies of 12 normotensive (group 1) and 12 preeclamptic (group 2) were immunolabeled with a rabbit anti-Ki67 antibody, a mouse anti-cytokeratin 18 and its neo-epitope, and a monoclonal cytodeath M30 antibody.

RESULTS

The immunoexpression of Ki67 for all trophoblast cell subpopulations within the myometrium was non-reactive in both study groups. Smooth muscle cells of the microvasculature reflected a moderate degree of proliferation in both groups. Morphometric image analysis of the wall of the spiral artery revealed a mean area of 31,1729 ± 51,180 µm(2) compared to 35,795 ± 8045 µm(2) in groups 1 and 2, respectively. An elevation of intramural trophoblast was evident within the spiral artery of group 1 (13%). Comparative analyses of M30 distribution on corresponding serial sections were 0.06% versus 0% in groups 1 and 2, respectively. The mean field area percentage of interstitial trophoblast invasion was 10.79% versus 2.87% with corresponding areas of apoptosis been 0.8 % versus 1.9 % in groups 1 and 2, respectively.

CONCLUSIONS

This study demonstrates an increased trophoblast apoptosis in placental bed of preeclamptic compared to normotensive pregnancies with concurrent absence of proliferation at term.

Reduced cystathionine γ-lyase and increased miR-21 expression are associated with increased vascular resistance in growth-restricted pregnancies: hydrogen sulfide as a placental vasodilator

Increased vascular impedance in the fetoplacental circulation is associated with fetal hypoxia and growth restriction. We sought to investigate the role of hydrogen sulfide (H₂S) in regulating vasomotor tone in the fetoplacental vasculature. H₂S is produced endogenously by catalytic activity of cystathionine β-synthase and cystathionine γ-lyase (CSE). Immunohistochemical analysis localized CSE to smooth muscle cells encircling arteries in stem villi. Immunoreactivity was reduced in placentas from pregnancies with severe early-onset growth-restriction and preeclampsia displaying abnormal umbilical artery Doppler waveforms compared with preeclamptic placentas with normal waveforms and controls. These findings were confirmed at the protein and mRNA levels. MicroRNA-21, which negatively regulates CSE expression, was increased in placentas with abnormal Doppler waveforms. Exposure of villus explants to hypoxia-reoxygenation significantly reduced CSE protein and mRNA and increased microRNA-21 expression. No changes were observed in cystathionine β-synthase expression, immunolocalized principally to the trophoblast, in pathologic placentas or in vitro. Finally, perfusion of normal placentas with an H₂S donor, after preconstriction with a thromboxane mimetic, resulted in dose-dependent vasorelaxation. Glibenclamide and N^G-nitro-l-arginine methyl ester partially blocked the effect, indicating that H₂S acts through ATP-sensitive K⁺ channels and nitric oxide synthesis. These results demonstrate that H₂S is a powerful vasodilator of the placental vasculature and that expression of CSE is reduced in placentas associated with increased vascular resistance.

Chronic glucocorticoid exposure potentiates placental chorionic plate artery constriction: implications for aberrant fetoplacental vascular resistance in fetal growth restriction

Fetal growth restriction (FGR) is a serious pregnancy complication, resulting in significant perinatal morbidity and mortality. Increased vascular resistance in the fetoplacental circulation is a hallmark of FGR and is associated with enhanced vasoconstriction of the resistance arteries in the placenta, the chorionic plate arteries (CPAs). Although the cause is unknown, FGR is associated with excess exposure to glucocorticoids (GCs), key mediators of vascular resistance in the systemic circulation. We hypothesized that GCs alter CPA reactivity, thereby contributing to the altered blood flow dynamics seen in FGR. We aimed to examine the acute and chronic effects of GCs on CPA reactivity and the operational mechanisms. Glucocorticoid receptors were highly expressed by CPA. 11β-Hydroxysteroid isoenzyme type 2 was detected within the endothelium, whereas 11β-hydroxysteroid isoenzyme type 1 was absent. Acute GC treatment significantly attenuated U46619-induced constriction. This effect was reversed by cotreatment with mifepristone or an endothelial NOS inhibitor. In contrast, chronic GC treatment potentiated U46619 constriction in a dose-dependent manner, which was partially abolished by mifepristone cotreatment. Similar effects were observed using a novel nonsteroidal glucocorticoid receptor-specific agonist. Chronic treatment with GCs altered the expression of several vasoactive factors, including thromboxane and bradykinin receptors, prokineticin-1, cyclooxygenase-2, and endothelial NOS. In summary, acute and chronic GC treatment exerts contrasting effects on CPA vasoreactivity. These opposing effects are consistent with temporal actions in other vascular beds and reflect activation of distinct nongenomic and genomic pathways. Chronic exposure to elevated GCs may contribute to the raised vascular resistance observed in the fetoplacental circulation in FGR.