Meconium-Associated Umbilical Vascular Myonecrosis: Correlations with Adverse Outcome and Placental Pathology

The Placenta and Neonatal Encephalopathy with a Focus on Hypoxic-Ischemic Encephalopathy

Background: Placental examination is important for its diagnostic immediacy to correlate with maternal and/or fetal complications and parturitional difficulties. In a broader context, clinicopathologic studies of the placenta have addressed a range of pathogenetic questions that have led to conclusive and inconclusive results and interpretations. Methods: Recent standardized morphologic criteria and terminology of placental lesions have facilitated the ability to compare findings from studies that have focused on complications and outcomes of pregnancy. This review is an evaluation of recent studies on placental lesions associated with hypoxic-ischemic encephalopathy (HIE). Conclusion: No apparent consensus exists on whether it is fetal inflammation with the release of cytokines or chronic maternal and/or fetal vascular malperfusion is responsible for HIE with a lowering of the threshold for hypoxic ischemia. The counter argument is that HIE occurs solely as an intrapartum event. Additional investigation is necessary.

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.

Placental Pathology and the Developing Brain

Abnormal neurodevelopmental outcomes are associated with multiple factors including prematurity, intrauterine infection, maternal comorbidities as well as fetal anomalies. Within the past decade, new standardized terminology in placental pathology has emerged, emphasizing the current understanding of processes that play a role in placental dysfunction. Factors playing a major role in the abnormal development of the placenta include abnormalities in blood flow and perfusion of the fetal and maternal compartments of the placenta termed fetal vascular malperfusion and maternal vascular malperfusion, respectively. Concepts reviewed include massive perivillous fibrin deposition, chronic villitis, meconium-associated injury as well as chorioamnionitis. Each have a temporal effect on the placental vascular tree and may reflect an altered maternal inflammatory response. In this article we highlight pathologic placental findings which when present can serve to explain, at least in part, altered neurodevelopment in the child, adolescent and adult. Lesions with a propensity for recurrence in future pregnancies are discussed.

Placental histology of acute versus continuous meconium exposure - Association with obstetric and neonatal outcomes

OBJECTIVE

We aimed to compare obstetric and neonatal outcomes of deliveries complicated by meconium stained amniotic fluid (MSAF), according to placental histology of continuous vs. acute meconium associated changes.

METHODS

This was a retrospective cohort study of singleton deliveries complicated by MSAF at a single university-affiliated medical center during 2008-2018. Obstetric and neonatal outcomes were compared between cases with placental acute vs. continuous meconium exposure associated changes (columnar epithelial changes and meconium-laden macrophages, respectively). Regression analysis was used to identify independent associations with adverse neonatal outcomes.

RESULTS

The medical records of 294 deliveries at our institution were reviewed, along with medical records of the neonates and the histopathological reports of their placentas. Ninety-two cases were classified as an acute placental reaction to meconium (acute exposure group) and 200 as continuous placental exposure (continuous exposure group). Patient demographics did not differ between groups. Placentas from the continuous exposure to meconium were associated with a higher rate of placental weight <10th percentile (p = 0.03) while the acute exposure group was associated with a shorter time between rupture of membranes and delivery (p = 0.02). and higher rates of non-reassuring fetal heart rate in labor (p = 0.003), and of adverse neonatal outcome (p = 0.02). In multivariable analysis adverse neonatal outcome was associated with acute histologic exposure to meconium independent of background confounders (aOR = 1.51, 95% CI 1.12-3.67).

CONCLUSIONS

Acute histological changes of MSAF were independently associated with adverse neonatal outcomes as compared to continuous histologic MSAF.

Predictors of High Grade and Other Clinically Significant Placental Findings by Indication for Submission in Singleton Placentas From Term Births

Indications for placental submission are variable. Established guidelines are largely based on expert opinion, and there is a need for more evidence-based criteria. A 10-year database of term placentas was used to evaluate indications significantly associated with placental pathology. Lesions in 5 categories were separated into high- and low-grade subgroups. Two additional high-grade lesions were also evaluated. Indications associated with high-grade placental lesions were chronic monitoring abnormalities, severe preeclampsia, pregestational diabetes, maternal signs of infection, postdates pregnancy, artificial reproductive technology, drug abuse, umbilical cord entanglements, selected gross placental abnormalities, stillbirth, Apgar 5 minutes <6, small-for-gestational age infant, and macrosomia. Indications for which placental findings did not differ from the population as a whole were acute monitoring abnormalities, chronic hypertension, maternal obesity, vaginal bleeding, accessory lobe/multilobed placenta, meconium-stained fluid, single umbilical artery, and borderline large-for-gestational age infant. Other indications for submission were intermediate showing significant or borderline elevations in the prevalence of low- and high-grade lesions combined. We suggest on the basis of this study that guidelines for the submission of singleton term placentas could be modified to exclude cases with clinical indications that lack a significant association with placental lesions.

Uncertainty over implications of placental histopathological findings: A survey of Australian and New Zealand neonatologists

AIM

Placental examination is known to provide useful information following an adverse pregnancy outcome. Despite existing literature and guidelines for placental examination; current workplace practices, attitudes towards the value of placental examination and the knowledge of perinatal clinicians regarding placental lesions of significance are unknown. The aim of the study is to explore the current knowledge of neonatologists and maternal fetal medicine specialists on placental histopathological findings and clinical management based on placental pathology.

METHODS

A total of 280 specialists working in perinatal centres across Australia and New Zealand were invited to complete a 20-question online multiple-choice-based survey addressing work-place placental examination practices, and participant beliefs regarding the utility of histopathological findings and follow-up practices.

RESULTS

A total of 74 neonatologists participated in the survey (28.2% response rate). Maternal fetal medicine specialists were excluded due to low response rate (2%). A total of 100% of respondents believed placental examination provided useful information regarding recent pregnancy and neonatal outcomes. They reported being aware of the presence of protocols for macroscopic examination of, and indications for histopathological examination of the placenta (55.4 and 54.1%, respectively). Nine neonatologists reported a system for actioning abnormal placental reports. There was no consensus amongst neonatologists as to which specific placental lesions held implications for future pregnancy or neonatal outcomes, and how these findings should be followed.

CONCLUSIONS

Our findings show placental examination is valued amongst neonatologists in Australia and New Zealand, but highlights the need for better education regarding the significance and utility of the results and what would be best practice for following up reports.

Isolated acute funisitis in the absence of acute chorioamnionitis: What does it mean?

OBJECTIVE

Acute funisitis (AF) is most commonly associated with acute chorioamnionitis (AC) and ascending infection. The significance of cases of AF without associated AC or isolated funisitis (IF) is unknown. Our objective was to evaluate clinical and pathologic features of IF and to determine its significance.

STUDY DESIGN

This was a retrospective review of placentas of patients delivering at our institution from 1997 to 2017. Placentas with the diagnosis of IF comprised the study population and placentas without either AF or AC served as controls.

RESULTS

There were 156 cases and 181 controls identified. Maternal age, gestational age, birthweight and mode of delivery were similar in both groups. 132 (84.6%) of cases of IF had meconium, with 62 (47.0%) having meconium only in the membranes, 36 (27.3%) in the membranes and cord and 34 (25.6%) in the membranes and cord with associated myonecrosis. 72 (38.7%) of controls had microscopically identified meconium, with only one (1.4%) showing meconium in the cord. None had myonecrosis (p < .001). There was also a significantly higher rate of intrauterine fetal demise (IUFD) in the IF group (p = .027). but the rate of suspected Intrauterine growth restriction (IUGR) was significantly greater in the controls (p = .014).

CONCLUSION

IF is highly associated with the presence of meconium discharge and meconium-associated myonecrosis of umbilical vessels. The inflammation in IF may be the result of damage to the muscle fibers of the cord due to meconium but additional studies are necessary to understand the significance of these findings.

Placental Lesions in Meconium Aspiration Syndrome

Background

Meconium aspiration syndrome (MAS) is defined by respiratory distress requiring supplemental oxygen in a meconium-stained neonate. MAS is clinically subclassified as mild, moderate, and severe according to the oxygen requirement. The aims of this study were to compare the histological findings in the placentas of MAS neonates with those of meconium-stained but non-MAS neonates and to analyze the correlation between the severity of MAS and the grade of its histological parameters.

Methods

We collected 160 singleton term placentas from neonates with meconium staining at birth from a tertiary medical center, Seoul, Republic of Korea. We reviewed hematoxylin and eosin sections of tissue samples (full-thickness placental disc, chorioamniotic membranes, and umbilical cord).

Results

Funisitis was present more frequently in MAS than in non-MAS (p < .01), of which the stage was correlated with the severity of MAS (p < .001). The histological findings consistent with maternal underperfusion and chronic deciduitis were more frequent in MAS than in non-MAS (p < .05). There was a correlation between the degree of chorionic vascular muscle necrosis and the severity of MAS (p < .05).

Conclusions

Our results suggest that fetal inflammatory response evidenced by funisitis occurs prenatally in MAS and that the stage of funisitis and of chorionic vascular muscle necrosis may be a predictive marker of the severity of MAS.