Altered Placental Chorionic Arterial Biomechanical Properties During Intrauterine Growth Restriction

PFAS alters placental arterial vasculature in term human placentae: A prospective pregnancy cohort study

INTRODUCTION

Perfluoroalkyl substances (PFAS) are synthetic chemicals used in industrial and consumer goods that are widely detected in human populations and are associated with adverse health outcomes, including perinatal health risks and child health. One mechanism of influence may be the impact of PFAS exposure on placental structure and function.

OBJECTIVES

The objective of this study is to investigate the relationship between maternal prenatal exposure to PFAS and measures of placental vascularization, and to assess whether changes in vascularization play a role in mediating the impact of PFAS on birth outcomes.

METHODS

Using data from a prospective cohort study, we examined associations between second trimester PFAS (individually and as mixtures using Bayesian kernel machine regression) and placental arterial vasculature in term placentae (N = 158); secondarily we evaluated the degree to which alterations in placental arterial vasculature explained associations between PFAS exposure and birth outcomes. Placental arterial vasculature features were collected from arterial tracings of each placental image.

RESULTS

In both linear regression and mixture models, natural log-transformed perfluorooctanoic acid concentrations were negatively associated with surface vasculature, indexed by the mean distance from arterial end point to perimeter (β = -0.23, 95% CI: -0.41, -0.041); additionally, maximum arterial tortuosity was negatively associated with placental weight (β = -0.19, 95% CI: -0.34, -0.051). There were no reliable differences in effect by fetal sex.

DISCUSSION

The findings provide some of the first evidence of PFAS exposure shaping a key measure of placental vascular function, which may underlie the impact of PFAS on perinatal and child health risks.

Large artery stiffening and mortality in a rat model of early vascular remodeling induced by intrauterine growth restriction and a high-fat diet

Intrauterine growth restriction (IUGR) and exposure to a high-fat diet (HFD) independently increase the risk of cardiovascular disease (CVD) and hyperlipidemia. In our previous studies, IUGR increased blood pressure and promoted vascular remodeling and stiffness in early life, a finding that persisted and was augmented by a maternal HFD through postnatal day (PND) 60. The impact of these findings with aging and the development of hyperlipidemia and atherosclerosis remain unknown. We hypothesized that the previously noted impact of IUGR on hypertension, vascular remodeling, and hyperlipidemia would persist. Adult female rats were fed either a regular diet (RD) or high fat diet (HFD) prior to conception through lactation. IUGR was induced by uterine artery ligation. Offspring were weaned to either RD or HFD through PND 365. For both control (C) and IUGR (I) and rats, this resulted in the following six groups per sex: offspring from RD dams weaned to an RD (CRR and IRR), or offspring from HFD dams weaned to either an RD (CHR and IHR) or to an HFD (CHH and IHH). IHH male and female rats had increased large artery stiffness, a suggestion of fatty streaks in the aorta, and persistent decreased elastin and increased collagen in the aorta and carotid arteries. Post-weaning HFD intake increased blood lipids regardless of IUGR status. IUGR increased HFD-induced mortality. We speculate that HFD-induced risk of CVD and mortality is potentiated by developmental programming of the ECM.

Ultrasound parameters of early pregnancy and Doppler indices of blood vessels in the placenta and umbilical cord throughout the pregnancy period in sheep

BACKGROUND

Ultrasonography is one of the most important techniques that enable the detection and monitoring of pregnancy. One such study using this technique is the assessment of the hemodynamics of fetal and umbilical blood vessels. However, there is little data on blood flow in the placentomes, which is the basic structural unit of the sheep's placenta. Therefore, the aim of this study was to determine the Doppler parameters in the arterial vessels of the caruncles, cotyledons and the umbilical cord as well as measuring venous flow rates during the entire gestation period of the sheep. Additionally, the usefulness of various other ultrasound parameters in the early diagnosis of pregnancy in sheep was analyzed.

RESULTS

Most of the Doppler parameters in umbilical, cotyledonary and caruncular arteries were significantly correlated with the day of pregnancy (p < 0.01). In the early stages of pregnancy, the peak systolic velocity (PSV), regardless of the location of the artery, was significantly lower than that in the later stages of pregnancy (p < 0.01). PSV was also found to be significantly higher in the umbilical artery than in the cotyledonary and caruncular arteries (p < 0.01). Until the 50th day of pregnancy, the end diastolic velocity (EDV) was not found in the umbilical and cotyledonary arteries. EDV was significantly higher in the caruncular arteries than in the cotyledonary and umbilical arteries (p < 0.01). The resistance index (RI) and pulsatility index (PI) in the early stages of pregnancy were found to be significantly higher than that in the later stages of pregnancy (p < 0.01). The RI and PI were significantly lower in the caruncular arteries than in the arteries of the cotyledons and umbilical cord (p < 0.01). In the umbilical vein, all Doppler parameters were observed to be significantly higher than those in the placentomal veins (p < 0.01 or p < 0.05). Using transrectal ultrasound, pregnancy was detected between 20 and 28 days after mating. The ovaries were observed to have corpora lutea, the diameter of which was fairly consistent from the 17th to the 56th day of pregnancy.

CONCLUSIONS

It has been demonstrated that both the location of the arterial vessel in the placental-umbilical circulation and the gestational age have a significant impact on hemodynamic parameters. The results also provide new insights about the blood flow in caruncular and cotyledonary arteries, which could contribute to a more holistic understanding of hemodynamic changes in the placentas of sheep. Analyzing haemodynamic parameters in the umbilical and placental veins are preliminary studies in sheep, but it could inspire further research in this field. Furthermore, the research conducted confirms the practicality and convenience of transrectal ultrasonography in the early diagnosis of pregnancy in sheep and also indicates that the identification and imaging of the corpus luteum using B-mode ultrasonography can be a very early and simple method of confirming effective mating in sheep.

A Review of Biomechanics Analysis of the Umbilical-Placenta System With Regards to Diseases

Placenta is an important organ that is crucial for both fetal and maternal health. Abnormalities of the placenta, such as during intrauterine growth restriction (IUGR) and pre-eclampsia (PE) are common, and an improved understanding of these diseases is needed to improve medical care. Biomechanics analysis of the placenta is an under-explored area of investigation, which has demonstrated usefulness in contributing to our understanding of the placenta physiology. In this review, we introduce fundamental biomechanics concepts and discuss the findings of biomechanical analysis of the placenta and umbilical cord, including both tissue biomechanics and biofluid mechanics. The biomechanics of placenta ultrasound elastography and its potential in improving clinical detection of placenta diseases are also discussed. Finally, potential future work is listed.

Multiscale and multimodal imaging of utero-placental anatomy and function in pregnancy

Placental structures at the nano-, micro-, and macro scale each play important roles in contributing to its function. As such, quantifying the dynamic way in which placental structure evolves during pregnancy is critical to both clinical diagnosis of pregnancy disorders, and mechanistic understanding of their pathophysiology. Imaging the placenta, both exvivo and invivo, can provide a wealth of structural and/or functional information. This review outlines how imaging across modalities and spatial scales can ultimately come together to improve our understanding of normal and pathological pregnancies. We discuss how imaging technologies are evolving to provide new insights into placental physiology across disciplines, and how advanced computational algorithms can be used alongside state-of-the-art imaging to obtain a holistic view of placental structure and its associated functions to improve our understanding of placental function in health and disease.

An increase in elastogenic components in the placental villi of women with chronic venous disease during pregnancy is associated with decreased EGFL7 expression level

Chronic venous disease (CVD) is the response to a series of hemodynamic changes in the venous system and the onset of this disease is often triggered by pregnancy. Placental tissue is particularly sensitive to the characteristic changes which occurs in venous hypertension. In this regard, changes in the extracellular matrix (ECM), that occur to adapt to this situation, are fundamental to controlling elastogenesis. Therefore, the aim of the present study was to analyze the changes that occur in the mRNA and protein expression level of proteins related to elastogenesis in the placental villi of women diagnosed with CVD, in the third trimester of pregnancy. An observational, analytical and prospective cohort study was conducted, in which the placenta from 62 women with CVD were compared with that in placenta from 52 women without a diagnosis of CVD. Gene and protein expression levels were analyzed using reverse transcription-quantitative PCR and immunohistochemistry, respectively. The results showed a significant decrease in the gene and protein expression level of EGFL7 in the placental villi of women with CVD. By contrast, significant increases in the gene and protein expression level of ECM-related proteins, such as tropoelastin, fibulin 4, fibrillin 1 and members of the lysyl oxidase family (LOX and LOXL-1) were also found in the placental villi of women with CVD. To the best of our knowledge, the results from the present study showed for the first time that CVD during pregnancy was associated with changes in the mRNA and protein expression level in essential components of the EGFL7-modulated elastogenesis process in placental villi.

Interpretation of wave reflections in the umbilical arterial segment of the feto-placental circulation: computational modeling of the feto-placental arterial tree

Placental vascular abnormalities are associated with a host of pregnancy complications including placenta mediated fetal growth restriction (FGR). Umbilical arterial (UA) Doppler ultrasound velocity waveforms are widely used in the diagnosis of underlying placental vascular abnormalities in pregnancies with suspected FGR, which greatly help prevent stillbirth via ongoing fetal monitoring and timely delivery. However, the sensitivity of UA Doppler diagnosis diminishes late in gestation. Our goal was to present a generalized wave decomposition method to compute forward and reflected components from UA waveforms. A detailed anatomical based model was also developed to explain observed UA flow waveform and to explore how vascular properties affect the shape of flow wave components. Using pregnant mice and high frequency ultrasound microscopy, we obtained in utero Doppler and M- mode ultrasound measurements in 15 fetuses UA. Following ultrasound, the placentas were collected and perfused with contrast agent to obtain high-resolution 3D images of the feto-placental arteries. Model results indicate the significant role of terminal load impedance (capillary and/or veins) in creating positive or negative reflected waveforms. A negative reflected waveform is obtained when terminal impedance increases. This is consistent with the elongated and non-branching terminal villi that are proposed cause the highly abnormal UA waveforms found in early-onset FGR. The significance of these findings for the diagnostic utility of UA Doppler in human pregnancy is that the identification and measurement of wave reflections may aid in discriminating between healthy and abnormal placental vasculature in pregnancies with suspected late-onset FGR.

Machine learning improves early prediction of small-for-gestational-age births and reveals nuchal fold thickness as unexpected predictor

OBJECTIVE

To investigate the performance of the machine learning (ML) model in predicting small-for-gestational-age (SGA) at birth, using second-trimester data.

METHODS

Retrospective data of 347 patients, consisting of maternal demographics and ultrasound parameters collected between the 20th and 25th gestational weeks, were studied. ML models were applied to different combinations of the parameters to predict SGA and severe SGA at birth (defined as 10th and third centile birth weight).

RESULTS

Using second-trimester measurements, ML models achieved an accuracy of 70% and 73% in predicting SGA and severe SGA whereas clinical guidelines had accuracies of 64% and 48%. Uterine PI (Ut PI) was found to be an important predictor, corroborating with existing literature, but surprisingly, so was nuchal fold thickness (NF). Logistic regression showed that Ut PI and NF were significant predictors and statistical comparisons showed that these parameters were significantly different in disease. Further, including NF was found to improve ML model performance, and vice versa.

CONCLUSION

ML could potentially improve the prediction of SGA at birth from second-trimester measurements, and demonstrated reduced NF to be an important predictor. Early prediction of SGA allows closer clinical monitoring, which provides an opportunity to discover any underlying diseases associated with SGA.

Hemodynamic consequences of incomplete uterine spiral artery transformation in human pregnancy, with implications for placental dysfunction and preeclampsia

Normal human pregnancy requires a dramatic increase in uteroplacental blood flow, which is achieved by a transformation in the geometry of uterine spiral arteries, a key element in this blood supply system. The transformation is mediated by trophoblast invasion directed at converting a portion of the spiral artery into an open funnel, thereby greatly reducing resistance to flow. The converted portion lies within the depth of the decidua and part of the myometrium. Insufficient depth of trophoblast invasion in early pregnancy predisposes to inadequate perfusion of the developing placenta and fetus and may lead to preeclampsia, fetal growth restriction, and preterm delivery, sometimes referred to as the "Great Obstetrical Syndromes." We examine the hemodynamic consequences of spiral artery transformation in human pregnancy and the relationship between the degree of transformation and the corresponding change in flow rate and resistance to flow. We identify two key variables in determining the hemodynamic change: the longitudinal converted fraction of the spiral artery and the relative downstream diameter of the open funnel. Our results indicate that there is a critical threshold in the value of the converted fraction required to achieve the marked increase in uteroplacental blood flow in normal pregnancy. This finding validates common clinical observations that the depth of trophoblast invasion reflects the "adequacy" of the increase in uteroplacental blood supply required in normal human pregnancy. Our results provide a quantitative measure of that adequacy and may serve as a future diagnostic marker for high-risk pregnancy.NEW & NOTEWORTHY Human pregnancy requires dramatic increase in uteroplacental blood supply achieved by geometric transformation of uterine spiral arteries and facilitated by trophoblast invasion of these arteries to greatly reduce resistance to flow. Incomplete transformation has been associated with failed pregnancies, preeclampsia, and other pathologies, but a quantitative measure of "incompleteness" has been unavailable so far. We use a mathematical model to obtain a numerical threshold for this measure which may serve as a future diagnostic marker.

The placenta in fetal growth restriction: What is going wrong?

The placenta is essential for the efficient delivery of nutrients and oxygen from mother to fetus to maintain normal fetal growth. Dysfunctional placental development underpins many pregnancy complications, including fetal growth restriction (FGR) a condition in which the fetus does not reach its growth potential. The FGR placenta is smaller than normal placentae throughout gestation and displays maldevelopment of both the placental villi and the fetal vasculature within these villi. Specialized epithelial cells called trophoblasts exhibit abnormal function and development in FGR placentae. This includes an altered balance between proliferation and apoptotic death, premature cellular senescence, and reduced colonisation of the maternal decidual tissue. Thus, the placenta undergoes aberrant changes at the macroscopic to cellular level in FGR, which can limit exchange capacity and downstream fetal growth. This review aims to compile stereological, in vitro, and imaging data to create a holistic overview of the FGR placenta and its pathophysiology, with a focus on the contribution of trophoblasts.