Color Doppler flow patterns and flow velocity waveforms of the intraplacental fetal circulation in growth-retarded fetuses

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.

Fetal Genotype for Specific Inherited Thrombophilias Is Not Associated With Severe Preeclampsia

OBJECTIVE

Little is known about the association between fetal thrombophilias and severe preeclampsia. The objective of this study was to examine the association between fetal genotype for factor V Leiden, prothrombin, and methylene tetrahydrofolate reductase (MTHFR) mutations and severe preeclampsia.

METHODS

Patients with severe preeclampsia or HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome admitted to Georgetown University Hospital were retrospectively identified. Controls were patients with uncomplicated, term deliveries. Fetal DNA was extracted from placental specimens and amplified by polymerase chain reaction (PCR) with locus-specific primers. The presence of polymorphisms was determined by enzymatic digestion with specific enzymes, and analyzed by polyacrylamide gels. Statistical analysis used Student t test for continuous variables and Fisher exact test for categorical data.

RESULTS

Patients with preeclampsia (n = 27) and controls (n = 17) were similar for maternal age, but, as expected, they were significantly different for gestational age at delivery, birth weight, Apgar scores at 5 minutes, rate of preterm delivery less than 37 weeks, and fetal growth restriction (all P <.05). DNA extraction was successful in 25 of 27 cases from the severe preeclampsia group and 14 of 17 controls. None of the placentas analyzed in the preeclamptic or control group revealed mutations in the factor V Leiden or prothrombin genes. There was no significant difference in the rate of fetuses heterozygous for MTHFR in the preeclampsia versus control group (48% vs 43%, P >.05).

CONCLUSION

In our study, fetal genotype for specific inherited thrombophilias does not appear to be associated with severe preeclampsia.

Intraplacental villous artery resistance indices and identification of placenta-mediated diseases

OBJECTIVE

Placenta-mediated diseases (PMDs) including preeclampsia and fetal growth restriction are often characterized by shallow trophoblast invasion and incomplete spiral artery remodeling leading to impaired placental perfusion. In this context, umbilical artery (UA) Doppler can be used to detect high resistance to flow characteristic of very late-stage placental disease. We propose that evaluation of intraplacental villous artery (IPVA) resistance can provide earlier detection of increased resistance in placental flow.

STUDY DESIGN

Seventy-five patients were recruited from the Ottawa Hospital. All had scans at 18 to 20, 28 and 34 weeks of gestation. IPVAs arising perpendicular to the chorionic plate in three regions (placental tips 4 cm away from cord insertion and within 1 cm from cord insertion) were sampled at each gestational age for resistance index (RI) and pulsatility index (PI). UA Doppler was also obtained from a free loop of cord. Pregnancy outcomes were collected from a chart review. Data were analyzed using SAS version 9.4 and standard statistic tests (mean±s.d., Student's t-test, mixed-effects modeling).

RESULT

A total of 53 patients completed the study. Of these, 38 had normal pregnancy outcomes (controls) and 15 (cases) developed PMD (preeclampsia, n=8 and low birth weight/intrauterine growth restriction, n=7). Mean birth weight in the study group was 2482.1±518.85 g. At 18 to 20, 28 and 34 weeks gestation, the mean IPVA resistance indices in the control group were 0.86±0.16, 0.81±0.12 and 0.71±0.12 for PI and 0.57±0.07, 0.55±0.06 and 0.49±0.06 for RI, respectively. However, in the cases developing PMDs, the PIs were 1.09±0.17, 0.95±0.21 and 0.78±0.07 and RIs 0.66±0.07, 0.60±0.07 and 0.54±0.04, respectively (P<0.05). UA PI and RI Doppler did not differ between the groups as early as 18 to 20 weeks gestation.

CONCLUSION

Doppler measures of IPVA appear superior to UA in detecting early changes related to PMD. IPVA PI and RI Doppler may be useful in the early identification of patients at risk of PMD.

Placental Volumetry by 2-D Sonography with a New Mathematical Formula: Prospective Study on the Shell of a Spherical Sector Model

The aim of this study was to determine the utility of a new mathematical model in volumetric assessment of the placenta using 2-D ultrasound. Placental volumetry was performed in a prospective cross-sectional survey by virtual organ computer-aided analysis (VOCAL) with the help of a shell-off method in 346 uncomplicated pregnancies according to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. Furthermore, placental thickness, length and height were measured with the 2-D technique to estimate placental volume based on the mathematical formula for the volume of "the shell of the spherical sector." Fetal size was also assessed by 2-D sonography. The placental volumes measured by 2-D and 3-D techniques had a correlation of 0.86. In the first trimester, the correlation was 0.82, and later during pregnancy, it was 0.86. Placental volumetry using "the circle-shaped shell of the spherical sector" mathematical model with 2-D ultrasound technique may be introduced into everyday practice to screen for placental volume deviations associated with adverse pregnancy outcome.

Can we use as a marker the maternal serum levels of D-dimer and fibrinogen to predict intra uterin growth restriction?

OBJECTIVE

The purpose of the present study was to assess the effect of D-dimer and fibrinogen levels in maternal serum as a marker for detection of intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

Two hundred-thirty four pregnant women who get pregnancy follow-up and delivery in the tertiary hospital between January 2011 and December 2011 were admitted to the study. Pregnant women were divided into two groups; group-1: 117 pregnants complicated with IUGR and group-2: 117 healthy pregnants without IUGR as control. Serum D-dimer and fibrinogen levels of all pregnant women were measured in the third trimester. The levels of D-dimer and fibrinogen were compared between two groups.

RESULTS

There is no significant difference between the groups for age, body mass index before pregnancy, smoking and gestational weeks (p>0.05). Gravidity, parity, number of children and maternal serum fibrinogen level were detected significantly different between the groups (p<0.001). D-dimer level was not significantly different between the groups (p=0.183), but fibrinogen level in group-1 was found higher than group-2.

CONCLUSION

Serum fibrinogen level was found higher in pregnant women complicated with IUGR but D-dimer level was not different between the groups. Although serum D-dimer should not be used as a marker for detection of IUGR, serum fibrinogen may be used.

MANAGEMENT OF REDUCED FETAL MOVEMENTS

Reduced fetal movement (RFM) is commonly defined as any reduction in maternal perception of fetal activity. Perceived fetal activity may be movement of limbs, trunk or head movement, but excludes fetal hiccoughs (as this is involuntary movement). The perception of fetal movement by an expectant mother is the first, and ongoing, non-sonographic indicator of fetal viability. The “normal” pattern of fetal movements varies from pregnancy to pregnancy, and often does not become established until 28 weeks’ gestation. Many babies have particularly active periods of the day, usually corresponding to periods of maternal rest and inactivity (which may in itself reflect increased maternal awareness of fetal movement). A variable percentage of sonographically observed fetal movements are perceived by prospective mothers (commonly 30–40%, although some studies report rates as high as 80%).

Fetal environment

The intrauterine environment has a strong influence on pregnancy outcome. The placenta and the umbilical cord together form the main supply line of the fetus. Amniotic fluid also serves important functions. These three main components decide whether there will be an uneventful pregnancy and the successful birth of a healthy baby. An insult to the intrauterine environment has an impact on the programming of the fetus, which can become evident in later life, mainly in the form of cardiovascular diseases, diabetes, and certain learning disabilities. The past two decades have witnessed major contributions from researchers in this field, who have included ultrasonologists, epidemiologists, neonatologists, and pediatricians. Besides being responsible for these delayed postnatal effects, abnormalities of the placenta, umbilical cord, and amniotic fluid also have associations with structural and chromosomal disorders. Population and race also influence pregnancy outcomes to some extent in certain situations. USG is the most sensitive imaging tool currently available for evaluation of these factors and can offer considerable information in this area. This article aims at reviewing the USG-related developments in this area and the anatomy, physiology, and various pathologies of the placenta, umbilical cord, and the amniotic fluid.

The effect of the postnatal environment on altered fetal programming of adult vascular function in mice that lack endothelial nitric oxide synthase

OBJECTIVE

The purpose of this study was to investigate vascular reactivity in heterozygous and homozygous offspring with a genetic predisposition for hypertension after postnatal cross-fostering to mothers with the opposite genetic inheritance of the NOS3 knockout allele.

STUDY DESIGN

Homozygous NOS3 knockout (C57BL/6J-NOS3(-/-KO)) and wild-type mice (NOS3(+/+WT)) were bred to obtain heterozygous litters with a paternally derived (NOS3(+/-pat)) or maternally derived (NOS3(+/-mat)) knockout allele. After delivery, heterozygous and homozygous litters were cross-fostered to a mother with the opposite NOS3 gene status. Carotid arteries were placed in a wire myograph for isometric tension recording with the use of contractile and relaxant agents. Statistical analysis with 1-way analysis of variance and Neuman-Keuls post-hoc testing was performed.

RESULTS

Increased sensitivity to phenylephrine and absent relaxation to acetylcholine in NOS3(+/-mat) was reversed with cross-fostering, and vasorelaxation to isoproterenol was increased. Contraction to calcium was increased in the cross-fostered paternally derived and wild-type litters.

CONCLUSION

Postnatal interventions may alter the adult vascular profile favorably that is the result of an abnormal intrauterine environment.

Prenatal diagnosis of fetal growth restriction

Fetal growth restriction is one of the most challenging obstetric problems. Due to confusing terminology, there is an obvious lack of uniform diagnostic criteria. At present, most authors do not distinguish between the terms 'small for gestational age' (SGA) and 'intra-uterine growth restriction' (IUGR). These two clinical entities are not the same. The term 'SGA' should be used for an infant who has failed to achieve a weight threshold (usually defined as the 10th percentile). Conversely, an IUGR infant has, by definition, not reached his/her genetic growth potential due to an insult that has occurred in utero. An IUGR fetus may or may not be SGA but it always implies a pathological process. Clinicians tend to manage both conditions in the same way by delivering affected cases, often by elective Caesarean section and often prematurely. This strategy obviously represents an overtreatment. This chapter will discuss the various aetiologies of small fetuses and will provide the reader with diagnostic tools to distinguish between subtypes.

A proinflammatory cytokine response is present in the fetal placental vasculature in placental insufficiency

OBJECTIVE

Vascular disease in the umbilical placental circulation is associated with fetal growth restriction and adverse outcome. It may be identified antenatally by the study of umbilical artery Doppler flow velocity waveforms. The cause of this vascular disease is unknown. We have previously provided indirect evidence for endothelial cell activation and a proinflammatory cytokine response. Recently, a family of inhibitors of cytokine signaling has been identified, referred to as the suppressors of cytokine signaling (SOCS). Activation of SOCS occurs when cytokines are produced in stimulated cells. We tested the hypothesis that endothelial cell activation was present in umbilical placental vascular disease and was associated with production of proinflammatory cytokines and members of the family of SOCS.

STUDY DESIGN

Placentas were collected at delivery and microvascular endothelial cells were isolated. We studied 13 normal pregnancies and 10 with umbilical placental vascular disease identified by an abnormal umbilical artery Doppler study. Placental pieces were digested with collagenase and purified by adherence to Dynabeads coated with monoclonal antibody against CD31. The RNA was extracted from isolated endothelial cells. The messenger RNA expression of cytokine production (interleukin-6 and interleukin-8) and the members of SOCS family (CIS, SOCS1, SOCS2, and SOCS3) were assessed by use of semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

In the microcirculation of the placenta, endothelial cell expression of interleukin-6 messenger RNA (2.50+/-0.60 vs 1.25+/-0.26) and interleukin-8 messenger RNA (2.83+/-0.55 vs 1.58+/-0.27) was up-regulated in umbilical placental vascular disease in comparison to normal pregnancy. The endothelial cell mRNA expression of SOCS2 (3.36+/-0.77 vs 1.76+/-0.29) and SOCS3 (2.77+/-0.60 vs 1.48+/-0.26) was enhanced in placental vascular disease. There was no significant difference in expression of CIS and SOCS1 in microvessel endothelial cells.

CONCLUSION

We have demonstrated that microvessel endothelium of the fetal placental vasculature produces both the proinflammatory cytokines (interleukin-6 and interleukin-8) and members of SOCS family (SOCS2 and SOCS3) in umbilical placental vascular disease. This cytokine production may play a key role in the interaction of endothelial cells of the placenta villi with neighboring cells. The up-regulation of SOCS2 and SOCS3 indicates these are the major negative regulators in umbilical placental microvessel endothelial cell activation pathways. By its occurrence, this also confirms the presence of a proinflammatory cytokine response.

Assessment of placental fractional moving blood volume using quantitative three-dimensional power doppler ultrasound

To test the hypothesis that the placental fractional moving blood volume is different with advancing gestational age (GA), we assessed the vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) of the placenta in normal pregnancy by using three-dimensional (3-D) power Doppler ultrasound (US). We enrolled 100 healthy pregnant women with gestational age between 20 to 40 weeks for this study. Three-dimensional power Doppler ultrasonography was used to assess the VI, FI and VFI in each case. Our results showed that the linear regression equations for VI, FI and VFI, by using GA as the independent variable, were VI = 0.27107 x GA -4.02748 (r = 0.84, p < 0.0001), FI = 0.56115 x GA + 34.28945 (r = 0.49, p < 0.001), and VFI = 0.15663 x GA -2.53810 (r = 0.82, p < 0.0001), respectively. In addition, the VI, FI and VFI values of the placental flow were also positively correlated with the fetal growth indices, namely, biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference and estimated fetal weight (all p values < 0.001). In conclusion, our study illustrates that the fractional moving blood volume of the placenta is positively correlated with the increment of gestational age and the fetal growth indices. Our data may be used as a reference in the assessment of the placental fractional moving blood volume using the quantitative 3-D power Doppler US.

Investigation of intraplacental villous arteries by Doppler flow imaging in growth-restricted fetuses

OBJECTIVE

The purposes of our study were to assess the ability of color and power Doppler sonography to depict the blood flow in the intraplacental villous arteries and to evaluate whether the blood flow of intraplacental villous arteries in a normal pregnancy is different from that in a pregnancy that is associated with intrauterine growth restriction.

STUDY DESIGN

Eighty-five women with uncomplicated pregnancy and 16 women with intrauterine growth-restricted fetuses between 27 and 38 weeks of gestation were examined by color and power Doppler imaging. The blood flow of intraplacental villous arteries was analyzed comparatively. The pulsatility index and peak systolic velocity were measured.

RESULTS

A unit of 1 intraplacental villous artery-1 and its branches were seen as 1 cotyledon by color and power Doppler imaging. The cotyledon was easily identified and counted. Each cotyledon contained only 1 intraplacental villous artery-1. This method can visualize the intraplacental villous artery-1 to intraplacental villous artery-4 in normal pregnancies. The terminal villous arteries beyond intraplacental villous artery-4 were not imaged. The number of detectable intraplacental villous artery-1 in 1 placenta in intrauterine growth restriction was significantly lower than that in normal pregnancy. The number of detectable branches in intrauterine growth restriction was also significantly lower than in normal pregnancy. No intraplacental villous artery-4 blood flow was found in women with intrauterine growth restriction. In examined arteries, pulsatility index decreased and peak systolic velocity increased significantly with advancing gestational age (P <.02). At any given gestational age, pulsatility index and peak systolic velocity in the peripheral arteries were significantly lower than those in the upstream arteries in normal pregnancy (P <.001). The pulsatility index value of each intraplacental villous artery was also lower than that of the umbilical artery in the women with intrauterine growth restriction (P <.05). There were no differences in pulsatility index in each artery between the groups, although there were a few high pulsatility index values in intrauterine growth restriction.

CONCLUSION

Color Doppler and power flow sonography are valuable tools for the detection of the blood flow of intraplacental villous arteries. The decrease in the number of detectable intraplacental villous artery-1 and branches was associated with intrauterine growth retardation.

Prostanoid production in the umbilicoplacental arterial tree relative to impaired glucose tolerance

The purpose of this study was to investigate prostanoid synthesis in different segments of the umbilicoplacental vascular tree and its relationship to impaired maternal glucose tolerance. Segments from the umbilical artery and vein, allantochorionic artery branches, and the cotyledon artery from 21 women with diabetes or impaired glucose tolerance and 10 healthy women were studied. Production of prostacyclin (PGI2) and thromboxane (TxA2) metabolites was determined. The Mann-Whitney U test, Wilcoxon signed-ranks matched-pairs test, Kruskal-Wallis test, analysis of variance, and simple linear regression analysis were used. A two-tailed P value of < 0.05 was considered statistically significant. From the umbilical artery distal to the cotyledon artery, the PGI2 synthesis decreased and the TxA2 synthesis increased gradually towards the periphery in normal pregnancy. The PGI2/TxA2 ratio was more than 200 times higher in the umbilical artery than in the cotyledon artery. The TxA2 production tended in general to be higher in the diabetic group than in the control group, resulting in significantly lower PGI2/TxA2 ratios in some vessels. The prostanoid production was not significantly correlated to maternal HbA1c or cord C-peptide concentrations. The balance between vascular prostacyclin and thromboxane synthesis in the umbilicoplacental arterial tree changed gradually towards the periphery: the more peripheral, the lower the prostacyclin and the higher the thromboxane production. The physiological role of this phenomenon is unknown, but may be of importance for the equilibration of vascular tone between arteries of different calibers. The altered prostanoid balance found in diabetic pregnancy was not directly attributable to the degree of maternal glycemic control, but may reflect increased free radical activity and peroxide production in diabetes.

Idiopathic fetal growth restriction: a pathophysiologic approach

Known causes of fetal growth restriction (FGR) can be traced in up to 40 percent of the cases. In the remainder of cases, FGR is idiopathic in origin. Evidence from experimental studies, antenatal findings at Doppler velocimetry of the uterine and umbilical arteries, and placental pathology studies suggests that idiopathic FGR can be divided into three groups: 1) primary abnormality in the uteroplacental perfusion; 2) primary abnormality in the fetoplacental perfusion; and 3) abnormal villous structure at the interface between fetal and maternal circulation. An improved understanding of the pathophysiology of idiopathic FGR is crucial to gain insight into its pathogenesis.