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

Abstract

Intrauterine passage of meconium is common, occurring in approximately 10-15% of term births. Uncommonly, long-standing meconium exposure is associated with umbilical vascular myonecrosis, but few studies have evaluated specific clinical and pathologic features. This is a retrospective study of 481 term placentas: 139 with meconium-associated myonecrosis, 139 with meconium in fetal membranes, only 62 with meconium in the cord without myonecrosis, and 139 controls without meconium. We studied clinical factors, including clinical evidence of meconium discharge, fetal distress, APGAR scores, intrauterine growth restriction (IUGR), and intrauterine fetal demise (IUFD), and histologic factors, including acute chorioamnionitis, umbilical cord complications, uteroplacental malperfusion, fetal thrombosis, chorangiosis, and fetal nucleated red blood cells. Meconium myonecrosis was significantly associated with clinical meconium, fetal distress, IUGR, IUFD, acute chorioamnionitis, cord complications, fetal thrombosis, chorangiosis, and nucleated red blood cells when compared to controls (P < 0.05). Compared to cases with meconium in the membranes only, clinical meconium, fetal distress, IUGR, chorioamnionitis, thrombosis, chorangiosis, and nucleated red blood cells remained significant. Compared to cases with meconium in the cord without myonecrosis, only chorioamnionitis retained significance. In conclusion, myonecrosis was associated with adverse clinical outcome and placental lesions associated with hypoxia. Chorioamnionitis was significantly more common in all meconium groups compared to controls. As myonecrosis is an important lesion, a clinical history of meconium should trigger a meticulous search for meconium and specifically myonecrosis.

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

“…MAVC, caused by prolonged exposure of fetal vascular smooth muscle cells to the toxic effects of bile acids in meconium, has been strongly associated with cerebral palsy and IUFD. 10,14,38 Although the number of affected cases was small, we found additional associations with postdates pregnancy, severe SGA, and an elevated fetoplacental weight ratio suggesting that uteroplacental insufficiency may play a synergistic role with meconium exposure in causing this lesion. Significantly elevated NRBC (more than 1 per high-power field) are believed to reflect prolonged fetal hypoxemia and have been associated with IUFD, severe FGR, neonatal encephalopathy, and cerebral palsy in previous studies.…”

Placental Lesions in Meconium Aspiration Syndrome

“…Chorionic vascular muscle necrosis can be diagnosed by observing eosinophilic cytoplasmic degeneration, nuclear pyknosis, discohesion, and rounding of peripheral vascular smooth muscle cells in vessels, resulting from apoptosis in chorionic vessels by prolonged meconium exposure [ 69 ]. It is associated with placental lesions resulting from hypoxia and poor neonatal outcome, including intrauterine growth restriction, intrauterine fetal demise, and fetal distress [ 70 ].…”

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

“…Other adverse pregnancy outcomes include growth restriction (6.4% of live births), prematurity (8% of live births) and neurodevelopmental disorders such as cerebral palsy (1.7/1000 births) . Histopathological analysis of the placenta can provide useful information following an adverse pregnancy outcome or suboptimal delivery conditions in many cases …”

“…3 Histopathological analysis of the placenta can provide useful information following an adverse pregnancy outcome or suboptimal delivery conditions in many cases. [4][5][6][7][8][9][10][11][12] Placental assessment can have clinical utility in four main ways: (i) provide information of relevance to immediate care of the mother or child (e.g. evidence of infection, vascular malperfusion) [4][5][6][7] ; (ii) prediction of possible recurrence of an outcome and providing opportunity for interventions to improve subsequent pregnancies (e.g.…”

“…[4][5][6][7][8][9][10][11][12] Placental assessment can have clinical utility in four main ways: (i) provide information of relevance to immediate care of the mother or child (e.g. evidence of infection, vascular malperfusion) [4][5][6][7] ; (ii) prediction of possible recurrence of an outcome and providing opportunity for interventions to improve subsequent pregnancies (e.g. chronic histocytic intervillositis, thrombophilias) [8][9][10][11][12] ; (iii) providing a diagnosis to explain adverse pregnancy outcomes (e.g.…”