To ignore or not to ignore placental calcifications on prenatal ultrasound: a systematic review and meta-analysis

Longitudinal associations between urinary biomarkers of phthalates and replacements with novel in vivo measures of placental health

STUDY QUESTION

What is the longitudinal association between gestational phthalate exposure and in vivo placental outcomes?

SUMMARY ANSWER

Phthalates were adversely associated with placental microvasculature, stiffness, and presence of calcification, with different metabolites associated with different outcomes.

WHAT IS KNOWN ALREADY

Phthalate exposure is ubiquitous and implicated as a contributor to adverse pregnancy outcomes, possibly through impacts on the placenta.

STUDY DESIGN, SIZE, DURATION

A total of 303 women were recruited in early pregnancy and prospectively followed for up to eight visits across gestation in the Human Placenta and Phthalates study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

At each visit, women provided urine samples and underwent placental ultrasounds. Urine was analyzed for 18 metabolites of phthalates and replacements. We took the geometric mean of repeated measurements to reflect pregnancy-averaged phthalate or replacement exposure for each participant (n = 303). Placental microvasculature, stiffness, and microcalcification presence were quantified from ultrasounds at each visit. Higher scores reflected worse placental function for all measures. Generalized linear mixed models were created to estimate the association between pregnancy-averaged exposure biomarker concentrations and repeated outcome measurements for microvasculature and stiffness. Gestational age at the time of calcification detection was modeled using Cox proportional hazards models.

MAIN RESULTS AND THE ROLE OF CHANCE

Monocarboxyisononyl phthalate and summed di(2-ethylhexyl) phthalate metabolites were associated with impaired microvasculature development, such that an interquartile range increase in concentration was associated with 0.11 standard deviation increase in the microvasculature ratio, indicating poorer vascularization (95% CI: 0.00, 0.22); 0.11 [95% CI: -0.01, 0.22], respectively. Monoethyl phthalate was associated with increased placental stiffness (0.09 [95% CI: -0.01, 0.19]) while summed di-iso-butyl phthalate metabolites and monobenzyl phthalate were associated with increased hazard of calcification detection (hazard ratios: 1.18 [95% CI: 0.98, 1.42]; 1.13 [95% CI: 0.96, 1.34]).

LIMITATIONS, REASONS FOR CAUTION

Outcomes used in this study are novel and further investigation is needed to provide clinical context and relevance.

WIDER IMPLICATIONS OF THE FINDINGS

We found evidence of associations between select phthalate biomarkers and various aspects of in vivo placental health, although we did not observe consistency across placental outcomes. These findings could illustrate heterogeneous effects of phthalate exposure on placental function.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported in part by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences (ZIA ES103344), and NIEHS T32ES007018. The authors declare that they have no competing interests to disclose. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Use of trade names is for identification only and does not imply endorsement by the CDC, the Public Health Service, or the US Department of Health and Human Services.

TRIAL REGISTRATION NUMBER

N/A.

Placental cartography of NADPH oxidase (NOX) family proteins: Involvement in the pathophysiology of preeclampsia

The placenta is an essential organ for fetal development. During the first trimester, it undergoes dramatic changes as it develops in an environment poor in oxygen (around 2-3%). From about 10 gestational weeks, oxygen levels increase to 8% in the intervillous chamber. These changes are accompanied by modulation of the activity of NADPH oxidase, a major source of production of reactive oxygen species in the first trimester of pregnancy. The NOX complex is composed of seven different proteins (NOX1-5 and DUOX1-2) whose placental involvements during physiological and pathological pregnancies are largely unknown. The aim of the study was to produce a cartography of NOX family proteins, in terms of RNA, protein expression, and localization during physiological pregnancy and in the case of preeclampsia (PE), in a cohort of early-onset PE (n = 11) and late-onset PE (n = 7) cases. NOX family proteins were mainly expressed in trophoblastic cells (NOX4-5, DUOX1) and modulated during physiological pregnancy. NOX4 underwent an unexpected and hitherto unreported nuclear translocation at term. In the case of PE, two groups stood out: NOX1-3, superoxide producers, were down-regulated (p < 0.05) while NOX4-DUOX1, hydrogen peroxide producers, were up-regulated (p < 0.05), compared to the control group. Mapping of placental NOX will constitute a reference and guide for future investigations concerning its involvement in the pathophysiology of PE.

Ultrasound Placental Remodeling Patterns and Pathology Characteristics in Patients with History of Mild SARS-CoV-2 Infection during Pregnancy

Introduction: This research aims to describe a progressive pattern of ultrasound placental remodeling in patients with a history of SARS-CoV-2 infection during pregnancy. Materials and Methods: This was a longitudinal, cohort study which enrolled 23 pregnant women with a history of former mild SARS-CoV-2 infection during the current pregnancy. Four obstetricians analyzed placental ultrasound images from different gestational ages following COVID infection and identified the presence and degree of remodeling. We assessed the inter-rater agreement and the interclass correlation coefficients. Pathology workup included placental biometry, macroscopic and microscopic examination. Results: Serial ultrasound evaluation of the placental morphology revealed a progressive pattern of placental remodeling starting from 30-32 weeks of gestation towards term, occurring approximately 8-10 weeks after the SARS-CoV-2 infection. Placental changes-the "starry sky" appearance and the "white line" along the basal plate-were identified in all cases. Most placentas presented normal subchorionic perivillous fibrin depositions and focal stem villi perivillous fibrin deposits. Focal calcifications were described in only 13% of the cases. Conclusions: We identified two ultrasound signs of placental remodeling as potential markers of placental viral shedding following mild SARS-CoV-2. The most likely pathology correspondence for the imaging aspect is perivillous and, respectively, massive subchorionic fibrin deposits identified in most cases.

Perinatal Outcomes in Premature Placental Calcification and the Association of a Color Doppler Study: Report from a Tertiary Care Hospital in Eastern India

Introduction: Placental calcification, identified before the 36th week of gestational age, is known as premature placental calcification (PPC). PPC could be a clue for the poor fetal outcome. However, its association with adverse perinatal outcomes is yet to be confirmed. Objective: The primary objective was to determine and compare the perinatal outcomes in pregnancies with and without documented premature placental calcification. Methodology: The present study was a prospective cohort study performed from October 2017 to September 2019. We consecutively enrolled 494 antenatal women who presented to our antenatal OPD after taking consent to participate in our study. Transabdominal sonographies were conducted between 28-36 weeks of gestation to document placental maturity. We compared maternal and fetal outcomes between those who were identified with grade III placental calcification (n = 140) and those without grade III placental calcification (n = 354). Results: The incidence of preeclampsia, at least one abnormal Doppler index, obstetrics cholestasis, placental abruption, and FGR (fetal growth restriction) pregnancies were significantly higher in the group premature placental calcification. We also found a significantly increased incidence of Low APGAR (Appearance, Pulse, Grimace, Activity, and Respiration) scores, NICU (Neonatal Intensive Care Unit) Admission, Abnormal CTG (cardiotocography), meconium-stained liquor, and low birth weight babies in those with grade III placental calcification. Conclusion: Clinicians should be aware of documenting placental grading while performing ultrasonography during 28 to 36 weeks. Ultrasonographically, the absence of PPC can define a subcategory of low-risk pregnant populations which probably need no referral to specialized centers and can be managed in these settings.

Ultrasound evaluation of the placenta in healthy and placental syndrome pregnancies: A systematic review

INTRODUCTION

An antepartum screening method to determine normal and abnormal placental function is desirable in the prevention of maternal and fetal pregnancy complications. Placental appearance can easily be obtained and evaluated using 2D ultrasonography, but surprisingly little is known about the change in placental appearance during gestation. Aim of this systematic review was to describe the antepartum placental appearance in placenta syndrome (PS) pregnancies, and to compare this to the appearance in healthy pregnancies.

METHODS

A systematic review investigating placental thickness, -lakes and/or -calcifications by ultrasound examination in both uncomplicated (reference group) and PS pregnancies in relation to gestational age was performed. English literature was searched using PubMed (NCBI), EMBASE (Ovid) and the Cochrane Library, from database inception until September 2020. Data on placental thickness was presented as a continuous variable or as the proportion of abnormal placental thickness. Data on placental lakes and -calcifications was presented as prevalence (%). There was no restriction applied on the definition of placental lakes or -calcifications. Due to heterogeneity, pooling of the results was not performed.

RESULTS

A total of 28 studies were included describing 1719 PS cases; consisting of 370 (21 %) cases with preeclampsia or pregnancy induced hypertension, 1341 (78 %) cases with fetal growth restriction (FGR) or small for gestational age (SGA), and 8 (1%) cases with combined clinical expressions. In addition, the reference group comprised 3315 pregnant women. Placental thickness showed an increase between the first and second trimester, which was higher in PS- compared to uncomplicated pregnancies. Placental lakes were frequently observed in FGR and SGA pregnancies, especially in the second trimester. Grade 3 calcifications were most prominent in the PS pregnancies, specifically in the late second and third trimester. Moreover, in the reference group, no grade 3 calcifications were reported before 35 weeks of gestation.

CONCLUSION

Placental appearance in PS-pregnancies shows higher placental thickness and greater presence of placental lakes and -calcifications compared to uncomplicated pregnancies. Standardized definitions of (ab-)normal placental appearance and longitudinal research in both healthy and complicated pregnancies are needed to improve personalized obstetric care.

Inorganic Phosphate in the Pathogenesis of Pregnancy-Related Complications

Inorganic phosphate (P_i) is an essential nutrient that fulfills critical roles in human health. It enables skeletal ossification, supports cellular structure and organelle function, and serves key biochemical roles in energetics and molecular signaling. P_i homeostasis is modulated through diet, intestinal uptake, renal reabsorption, and mobilization of stores in bone and extracellular compartments. Disrupted P_i homeostasis is associated with phosphate wasting, mineral and bone disorders, and vascular calcification. Mechanisms of Pi homeostasis in pregnancy remain incompletely understood. The study presented herein examined biological fluid Pi characteristics over the course of gestation. Correlations with gestation age, pregnancy number, preterm birth, preeclampsia, diabetes mellitus, and placental calcification were evaluated during the last trimester. The results support that maternal urinary P_i levels increased during the third trimester of pregnancy. Reduced levels were observed with previous pregnancy. Amniotic fluid P_i levels decreased with gestation while low second trimester levels associated with preterm birth. No significant difference in urinary P_i levels was observed between preeclampsia and controls (8.50 ± 2.74 vs. 11.52 ± 2.90 mmol/L). Moreover, increased maternal urinary P_i was associated with preexisting diabetes mellitus in preeclampsia. Potential confounding factors in this study are maternal age at delivery and body mass index (BMI)—information which we do not have access to for this cohort. In conclusion, P_i levels provide clinical information regarding the pathogenesis of pregnancy-related complications, supporting that phosphate should be examined more closely and in larger populations.

Experimental Infection of Mid-Gestation Pregnant Female and Intact Male Sheep with Zika Virus

Zika virus (ZIKV) is an arbovirus that causes birth defects, persistent male infection, and sexual transmission in humans. The purpose of this study was to continue the development of an ovine ZIKV infection model; thus, two experiments were undertaken. In the first experiment, we built on previous pregnant sheep experiments by developing a mid-gestation model of ZIKV infection. Four pregnant sheep were challenged with ZIKV at 57–64 days gestation; two animals served as controls. After 13–15 days (corresponding with 70–79 days of gestation), one control and two infected animals were euthanized; the remaining animals were euthanized at 20–22 days post-infection (corresponding with 77–86 days of gestation). In the second experiment, six sexually mature, intact, male sheep were challenged with ZIKV and two animals served as controls. Infected animals were serially euthanized on days 2–6 and day 9 post-infection with the goal of isolating ZIKV from the male reproductive tract. In the mid-gestation study, virus was detected in maternal placenta and spleen, and in fetal organs, including the brains, spleens/liver, and umbilicus of infected fetuses. Fetuses from infected animals had visibly misshapen heads and morphometrics revealed significantly smaller head sizes in infected fetuses when compared to controls. Placental pathology was evident in infected dams. In the male experiment, ZIKV was detected in the spleen, liver, testes/epididymides, and accessory sex glands of infected animals. Results from both experiments indicate that mid-gestation ewes can be infected with ZIKV with subsequent disruption of fetal development and that intact male sheep are susceptible to ZIKV infection and viral dissemination and replication occurs in highly vascular tissues (including those of the male reproductive tract).

Safety and efficacy of ChAdOx1 RVF vaccine against Rift Valley fever in pregnant sheep and goats

Rift Valley fever virus (RVFV) is a zoonotic mosquito-borne virus that was first discovered in Kenya in 1930 and has since spread to become endemic in much of Africa and the Arabian Peninsula. Rift Valley fever (RVF) causes recurrent outbreaks of febrile illness associated with high levels of mortality and poor outcomes during pregnancy-including foetal malformations, spontaneous abortion and stillbirths-in livestock, and associated with miscarriage in humans. No vaccines are available for human use and those licensed for veterinary use have potential drawbacks, including residual virulence that may contraindicate their use in pregnancy. To address this gap, we previously developed a simian adenovirus vectored vaccine, ChAdOx1 RVF, that encodes RVFV envelope glycoproteins. ChAdOx1 RVF is fully protective against RVF in non-pregnant livestock and is also under development for human use. Here, we now demonstrate that when administered to pregnant sheep and goats, ChAdOx1 RVF is safe, elicits high titre RVFV neutralizing antibody, and provides protection against viraemia and foetal loss, although this protection is not as robust for the goats. In addition, we provide a description of RVFV challenge in pregnant goats and contrast this to the pathology observed in pregnant sheep. Together, our data further support the ongoing development of ChAdOx1 RVF vaccine for use in livestock and humans.

Pathological Mineralization: The Potential of Mineralomics

Pathological mineralization has been reported countless times in the literature and is a well-known phenomenon in the medical field for its connections to a wide range of diseases, including cancer, cardiovascular, and neurodegenerative diseases. The minerals involved in calcification, however, have not been directly studied as extensively as the organic components of each of the pathologies. These have been studied in isolation and, for most of them, physicochemical properties are hitherto not fully known. In a parallel development, materials science methods such as electron microscopy, spectroscopy, thermal analysis, and others have been used in biology mainly for the study of hard tissues and biomaterials and have only recently been incorporated in the study of other biological systems. This review connects a range of soft tissue diseases, including breast cancer, age-related macular degeneration, aortic valve stenosis, kidney stone diseases, and Fahr’s syndrome, all of which have been associated with mineralization processes. Furthermore, it describes how physicochemical material characterization methods have been used to provide new information on such pathologies. Here, we focus on diseases that are associated with calcium-composed minerals to discuss how understanding the properties of these minerals can provide new insights on their origins, considering that different conditions and biological features are required for each type of mineral to be formed. We show that mineralomics, or the study of the properties and roles of minerals, can provide information which will help to improve prevention methods against pathological mineral build-up, which in the cases of most of the diseases mentioned in this review, will ultimately lead to new prevention or treatment methods for the diseases. Importantly, this review aims to highlight that chemical composition alone cannot fully support conclusions drawn on the nature of these minerals.

Placental Vascular Calcification and Cardiovascular Health: It Is Time to Determine How Much of Maternal and Offspring Health Is Written in Stone

Vascular calcification is the deposition of calcium phosphate minerals in vascular tissue. Vascular calcification occurs by both active and passive processes. Extent and tissue-specific patterns of vascular calcification are predictors of cardiovascular morbidity and mortality. The placenta is a highly vascularized organ with specialized vasculature that mediates communication between two circulatory systems. At delivery the placenta often contains calcified tissue and calcification can be considered a marker of viral infection, but the mechanisms, histoanatomical specificity, and pathophysiological significance of placental calcification are poorly understood. In this review, we outline the current understanding of vascular calcification mechanisms, biomedical consequences, and therapeutic interventions in the context of histoanatomical types. We summarize available placental calcification data and clinical grading systems for placental calcification. We report on studies that have examined the association between placental calcification and acute adverse maternal and fetal outcomes. We then review the intersection between placental dysfunction and long-term cardiovascular health, including subsequent occurrence of maternal vascular calcification. Possible maternal phenotypes and trigger mechanisms that may predispose for calcification and cardiovascular disease are discussed. We go on to highlight the potential diagnostic value of placental calcification. Finally, we suggest avenues of research to evaluate placental calcification as a research model for investigating the relationship between placental dysfunction and cardiovascular health, as well as a biomarker for placental dysfunction, adverse clinical outcomes, and increased risk of subsequent maternal and offspring cardiovascular events.