Pathologic Assessment of the Placenta

Clinical Significance of the Large Fetal Vessel Lesions in Placental Fetal Vascular Malperfusion

Fetal vascular malperfusion (FVM) is an important pattern of placental injury. Although the significance of distal villous FVM (clusters of sclerotic and/or mineralized chorionic villi) is well documented, the clinical significance of proximal (large vessel) lesions of FVM is less clear, which is the aim of this retrospective analysis. To evaluate the clinical significance and placental associations of single and coexisting categories of lesions of large vessel FVM, 24 clinical and 44 placental phenotypes of 804 consecutive placentas with at least 1 lesion of proximal vessel FVM from the second half of pregnancy, divided according to the type or category of the individual FVM lesion (fetal vascular ectasia, fetal vascular thrombi, intramural fibrin deposition, and stem vessel obliteration): 689, 341, 286, and 267 placentas, respectively (first analysis) and single or coexisting large fetal vessel lesions (1, 2, 3, and 4 coexisting categories of lesions: 276, 321, 162, and 45 placentas, respectively) were statistically compared (analysis of variance, χ2, univariate analysis). Because of multiple comparisons, Bonferroni-corrected P < .001 was used as a threshold of statistical significance. In this population of high-risk pregnancies dominated by fetal congenital anomalies, single individual or 1 to 2 coexisting categories of lesions of the large vessel FVM, including fetal vascular thrombi, did not consistently correlate with clinical or placental variables and were not prognostically useful, but the coexistence of 3 or 4 lesions was associated with the most advanced gestational age, fetal congenital anomalies, distal villous FVM, particularly high-grade, chorangioma or chorangiomatosis, hypercoiled umbilical cord, perivascular stem edema, and marginate or vallate placenta. Therefore, the finding of multiple lesions of the large vessel FVM not only merits a diligent search for the distal villous lesions including the CD34 immunostaining, but also justifies putting the large vessel (global) FVM on the final placental diagnosis line, which in the case of up to only 2 lesions may not be justified.

Placental fetal vascular malperfusion, neonatal neurologic morbidity, and infant neurodevelopmental outcomes: a systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the association of placental fetal vascular malperfusion lesions with neonatal brain injury and adverse infant neurodevelopmental outcomes.

DATA SOURCES

PubMed and Medline, Scopus, and Cochrane databases were searched from inception to July 2022.

STUDY ELIGIBILITY CRITERIA

We included cohort and case-control studies reporting the associations of fetal vascular malperfusion lesions with neonatal encephalopathy, perinatal stroke, intracranial hemorrhage, periventricular leukomalacia, and infant neurodevelopmental and cognitive outcomes.

METHODS

Data were analyzed by including fetal vascular malperfusion lesions as an exposure variable and brain injuries or neurodevelopmental impairment as outcomes using random-effects models. The effect of moderators, such as gestational age or study type, was assessed by subgroup analysis. Study quality and risk of bias were assessed by applying the Observational Study Quality Evaluation method.

RESULTS

Out of the 1115 identified articles, 26 were selected for quantitative analysis. The rates of neonatal central nervous system injury (neonatal encephalopathy or perinatal stroke) in term or near-term infants were more common among fetal vascular malperfusion cases (n=145) than among controls (n=1623) (odds ratio, 4.00; 95% confidence interval, 2.72-5.90). In premature deliveries, fetal vascular malperfusion lesions did not influence the risk of intracranial hemorrhage or periventricular leukomalacia (odds ratio, 1.40; 95% confidence interval, 0.90-2.18). Fetal vascular malperfusion-associated risk of abnormal infant neurodevelopmental outcome (314 fetal vascular malperfusion cases and 1329 controls) was modulated by gestational age being higher in term infants (odds ratio, 5.02; 95% confidence interval, 1.59-15.91) than in preterm infants (odds ratio, 1.70; 95% confidence interval, 1.13-2.56). Abnormal infant cognitive development and mental development were more common among fetal vascular malperfusion cases (n=241) than among controls (n=2477) (odds ratio, 2.14; 95% confidence interval, 1.40-3.27). The type of study (cohort vs case-control) did not influence the association between fetal vascular malperfusion and subsequent infant brain injury or abnormal neurodevelopmental outcome.

CONCLUSION

The findings of cohort and case-control studies indicate a considerable association between fetal vascular malperfusion placental lesions and increased risk of brain injury in term neonates, and neurodevelopmental impairment in both term and preterm infants. A diagnosis of placental fetal vascular malperfusion should be taken into consideration by both pediatricians and neurologists during the follow-up of infants at risk of adverse neurodevelopmental outcomes.

Comparison of Placental Pathology Reports From Spontaneous Preterm Births Finalized by General Surgical Pathologists Versus Perinatal Pathologist: A Call to Action

Placental examination, frequently performed by general surgical pathologists, plays an important role in understanding patient outcomes and explaining the underlying mechanisms leading to preterm birth (PTB). This secondary analysis of a larger study recurrent PTB aimed to compare diagnoses between general surgical pathologists (GSP) and a perinatal pathologist (PP) in preterm placentas examined between 2009 and 2018 at a single institution. Pathology diagnoses were coded into 4 categories (acute inflammation [AI], chronic inflammation, fetal vascular malperfusion, maternal vascular malperfusion) based on original reports for the GSP and second review by the single PP. A total of 331 placentas were included, representing placentas finalized by 17 GSPs. The prevalence of all 4 placental diagnostic categories was higher for the PP, and nearly half (49.2%) of placentas finalized by GSP had no diagnostic findings. Agreement was highest for AI at κ=0.50 (weak agreement). However, there was no agreement for maternal vascular malperfusion (κ=0.063), chronic inflammation (κ=0.0026), and fetal vascular malperfusion (κ = -0.018). Chronic basal deciduitis with plasma cells had the highest false-negative rate (missed in 107 cases by GSP). Villous infarction had the highest false-positive rate (overcalled in 28/41 [68%] cases) with the majority of the "infarcts" representing intervillous thrombi. In conclusion, there is no agreement between GSP and PP when assessing placental pathology other than AI, and weak agreement even for AI. These findings are a call to action to implement educational efforts and structural/organizational changes to improve consistency of placental pathology reporting.

Placental pathology in perinatal asphyxia: a case-control study

Introduction

Placentas of term infants with birth asphyxia are reported to have more lesion such as maternal vascular malperfusion (MVM), fetal vascular malperfusion (FVM) and chorioamnionitis with fetal response (FIR) than those of term infants without birth asphyxia. We compared the placental pathology of asphyxiated newborns, including those who developed hypoxic-ischemic encephalopathy (HIE), with non-asphyxiated controls.

Methods

We conducted a retrospective case-control study of placentas from neonates with a gestational age ≥ 35 weeks, a birthweight ≥ 1,800 g, and no malformations. Cases were asphyxiated newborns (defined as those with an umbilical artery pH ≤ 7.0 or base excess ≤ -12 mMol, 10-minute Apgar score ≤ 5, or the need for resuscitation lasting >10 min) from a previous cohort, with (n=32) and without (n=173) diagnosis of HIE. Controls were non-asphyxiated newborns from low-risk l (n= 50) or high-risk (n= 68) pregnancies. Placentas were analyzed according to the Amsterdam Placental Workshop Group Consensus Statement 2014.

Results

Cases had a higher prevalence of nulliparity, BMI>25, thick meconium, abnormal fetal heart monitoring, and acute intrapartum events than controls (p<0.001). MVM and FVM were more frequent among non-asphyxiated than asphyxiated newborns (p<0.001). There was no significant difference in inflammatory lesions or abnormal umbilical insertion site. Histologic meconium-associated changes (MAC) were observed in asphyxiated newborns only (p= 0.039).

Discussion

Our results confirm the role of antepartum and intrapartum risk factors in neonatal asphyxia and HIE. No association between neonatal asphyxia and placental lesions was found, except for in the case of MAC. The association between clinical and placental data is crucial to understanding and possibly preventing perinatal asphyxia in subsequent pregnancies.

Patterns of placental pathology associated with preeclampsia

INTRODUCTION

Maternal vascular malperfusion (MVM) is commonly observed in early onset preeclampsia, but less prevalent in late onset preeclampsia. The purpose of our analysis was to investigate patterns of placental pathology in preeclampsia.

METHODS

Electronic health records for all singleton livebirths from 2009 to 2018 at a single institution with a diagnosis of preeclampsia were obtained. Text searching was used to obtain placental data from pathology reports, including lesions of MVM, fetal vascular malperfusion (FVM), chronic inflammation (CI), and acute inflammation (AI). Placental pathology was compared based on timing of delivery and latent class analysis (LCA) was used to investigate subtypes of preeclampsia based on 22 placental variables.

RESULTS

728 patients were included in the analysis. Prevalence of MVM decreased with advancing gestation (95.4% at <34 weeks, 69.8% at 34-36 weeks, and 50%, ≥37 weeks; p < 0.01). LCA identified five classes based on placental pathology: (1) high grade MVM, (2) CI and FVM, (3) low grade MVM, (4) AI, (5) other. Preterm birth varied across the classes (p < 0.01), with the highest prevalence observed among the classes characterized by MVM (high grade: 87.6%; low grade: 63.0%) and the lowest prevalence among the class characterized by AI (23.5%).

DISCUSSION

Placental pathology in preeclampsia differs based on gestational age at delivery with MVM seen in nearly all early onset preeclampsia cases. Latent classes largely grouped by previously defined patterns of placental injury (MVM, CI, FVM, AI), and again revealed the highest likelihood of preterm birth in classes characterized by MVM. Results suggest there may be multiple mechanisms leading to the clinical manifestations of preeclampsia.

Placental pathology is necessary to understand common pregnancy complications and achieve an improved taxonomy of obstetrical disease

The importance of a fully functioning placenta for a good pregnancy outcome is unquestioned. Loss of function can lead to pregnancy complications and is often detected by a thorough placental pathologic examination. Placental pathology has advanced the science and practice of obstetrics and neonatal-perinatal medicine by classifying diseases according to underlying biology and specific patterns of injury. Many past obstacles have limited the incorporation of placental findings into both clinical studies and day-to-day practice. Limitations have included variability in the nomenclature used to describe placental lesions, a shortage of perinatal pathologists fully competent to analyze placental specimens, and a troubling lack of understanding of placental diagnoses by clinicians. However, the potential use of placental pathology for phenotypic classification, improved understanding of the biology of adverse pregnancy outcomes, the development of treatment and prevention, and patient counseling has never been greater. This review, written partly in response to a recent critique published in a major obstetrics-gynecology journal, reexamines the role of placental pathology by reviewing current concepts of biology; explaining the most recent terminology; emphasizing the usefulness of specific diagnoses for obstetrician-gynecologists, neonatologists, and patients; previewing upcoming changes in recommendations for placental submission; and suggesting future improvements. These improvements should include further consideration of overall healthcare costs, cost-effectiveness, the clinical value added of placental assessment, improvements in placental pathology education and practice, and leveraging of placental pathology to identify new biomarkers of disease and evaluate novel therapies tailored to specific clinicopathologic phenotypes of both women and infants.

Criteria for placental examination for obstetrical and neonatal providers

Pathologic examination of the placenta can provide insight into likely (and unlikely) causes of antepartum and intrapartum events, diagnoses with urgent clinical relevance, prognostic information for mother and infant, support for practice evaluation and improvement, and insight into advancing the sciences of obstetrics and neonatology. Although it is true that not all placentas require pathologic examination (although alternative opinions have been expressed), prioritization of placentas for pathologic examination should be based on vetted indications such as maternal comorbidities or pregnancy complications in which placental pathology is thought to be useful for maternal or infant care, understanding pathophysiology, or practice modifications. Herein we provide placental triage criteria for the obstetrical and neonatal provider based on publications and expert opinion of 16 placental pathologists and a pathologists' assistant, formulated using a modified Delphi approach. These criteria include indications in which placental pathology has clinical relevance, such as pregnancy loss, maternal infection, suspected abruption, fetal growth restriction, preterm birth, nonreassuring fetal heart testing requiring urgent delivery, preeclampsia with severe features, or neonates with early evidence of multiorgan system failure including neurologic compromise. We encourage a focused gross examination by the provider or an attendant at delivery for all placentas and provide guidance for this examination. We recommend that any placenta that is abnormal on gross examination undergo a complete pathology examination. In addition, we suggest practice criteria for placental pathology services, including a list of critical values to be used by the relevant provider. We hope that these sets of triage indications, criteria, and practice suggestions will facilitate appropriate submission of placentas for pathologic examination and improve its relevance to clinical care.

A comprehensive analysis of the association between placental pathology and recurrent preterm birth

BACKGROUND

Histologic examination of the placenta is often performed after preterm birth. Although placental examination cannot change the index pregnancy outcome, it may inform the risk of adverse outcomes in a subsequent pregnancy. Previous research has examined the association between individual histologic lesions and pregnancy outcomes without consistent results.

OBJECTIVE

This study aimed to determine the independent contributions of the major placental pathology histologic types to recurrent preterm birth.

STUDY DESIGN

This was a retrospective cohort study of deliveries at a tertiary care center from January 2009 to March 2018. Individuals with ≥2 births, an index birth of <37 weeks of gestation, and a placental pathology report from the index pregnancy were included. The presence of maternal vascular malperfusion, fetal vascular malperfusion, acute inflammation, and chronic inflammation was extracted from the pathology reports for each index placenta and classified as none, low grade, or high grade. A log-binomial model incorporating all 4 placental pathology histologic types, index gestational age, race, and maternal age was used to estimate the associations between each placental histologic type and risk of recurrent preterm birth. Moreover, 2-way interaction terms were studied among placental histologic types. In addition, 2 stratified analyses were completed on the basis of characteristics of the index preterm birth: (1) by late preterm (gestational age of 34-36 weeks) vs early-to-moderate preterm birth (<34 weeks) and (2) a subgroup analysis of those with spontaneous preterm birth.

RESULTS

A total of 924 pregnancy pairs met the inclusion criteria. Only high-grade chronic inflammation was independently associated with an increased risk of recurrent preterm birth (adjusted risk ratio, 1.37; 95% confidence interval, 1.03-1.81). Stratified analysis by gestational age group demonstrated maternal vascular malperfusion was associated with recurrent preterm birth only among those with early preterm birth (adjusted risk ratio, 1.40; 95% confidence interval, 1.01-1.93). Among participants with spontaneous preterm labor, no association was found between pathology histologic types and risk of preterm birth.

CONCLUSION

Among index preterm pregnancies, high-grade chronic placental inflammation was associated with recurrent preterm birth. Low-grade maternal vascular malperfusion was associated with recurrent preterm birth only among those with an early or moderate index preterm birth (<34 weeks of gestation). These findings may be useful in determining the risk profile for individual patients and may generate hypotheses as to the pathogenesis of recurrent preterm birth.