Trophoblastic and subtrophoblastic mineral salt deposition in hydramnios

Segmental villous mineralization: A placental feature of fetal vascular malperfusion

INTRODUCTION

This retrospective analysis was performed to find out if clusters of mineralized chorionic villi can be regarded as an independent feature of fetal vascular malperfusion (FVM).

METHODS

Of all 1698 placentas reviewed by the author during the last 10 years, 39 (2.3%) showed clusters of mineralized chorionic villi (Group 1), 100 cases (5.9%) showed randomly scattered mineralized chorionic villi with without clustering (Group 2), and the remaining 1559 placentas showed no villous mineralization (comparative Group 3). In doubtful cases, histochemistry stains were performed to determine the pattern of villous mineralization. Twenty three independent clinical and 43 placental variables were statistically compared among the groups: descriptive statistics (Chi-square, Fisher test or signed rank test), and logistics regression model.

RESULTS

Clinically, Group 1 featured shorter gestational age than Group 2, and in addition to shorter gestational age, more common oligohydramnios, polyhydramnios, induction of labor, macerated stillbirth and fetal growth restriction than Group 3. Of placental variables, fetal vascular ectasia, and clusters of avascular chorionic villi were more common in Group 1 than in Group 2, and in addition, segmental villous stromal vascular karyorrhexis was more common than in Group 3. By the logistics regression mode, segmental villous mineralization was independently associated with other histological features of FVM as a group and particularly with clusters of sclerotic chorionic villi.

DISCUSSION

FVM is characterized by temporal heterogeneity, i.e. coexistence of lesions of various duration, and strongly and independently correlates with clusters of mineralized chorionic villi. Therefore, segmental villous mineralization should be included into the category of segmental FVM. It can be seen even in totally fibrotic placentas of prolonged stillbirth when other histological features of segmental vascular malperfusion can be obscured by global villous sclerosis.

Value of autopsy in nonimmune hydrops fetalis: series of 51 stillborn fetuses

Nonimmune hydrops fetalis (NIHF) is used to describe fetuses and newborns with generalized edema and cavity effusions. It is helpful to alert physicians about the presence of anemia, heart failure, and/or hypoproteinemia, but this diagnosis is frequently overlooked. We reviewed the autopsy files from 1990 to 2000, selected all cases with NIHF including clinical information (with maternal laboratory tests and ultrasound), and classified patients by etiology. Among 840 stillborn autopsies during the 11-year period, we found 51 with NIHF (6.07%). The clinical summary had mentioned hydrops in 14 patients and the etiology in another 7 by fetal ultrasonography, but without addressing the possibility of hydrops. In the remaining 30 cases neither hydrops nor an etiology was mentioned. Other pertinent diagnoses were maternal diabetes mellitus (4), congenital heart disease (3), and cystic hygroma (2). The following diagnoses were made in one instance each: cardiac tumor, twin transfusion syndrome, congenital adenomatoid malformation, syphilis, Turner syndrome, and cerebral arteriovenous malformation. Postmortem and placental examination confirmed the following etiologies: congenital infections (17); placental pathology significant enough to explain NIHF (10); cardiovascular diseases (8) (further classified as congenital heart disease [3], rhabdomyoma [1], and vascular malformations [4]); chromosomal abnormalities (6); uncontrolled maternal diabetes (4); intrathoracic lesions (2); prune-belly syndrome (2); and idiopathic NIHF (2). Only 3.9% of the cases studied had no identifiable etiology. The cause of hydrops was confirmed by autopsy in 47 fetuses (92%), which further supports the importance of performing an autopsy. Thirty-two cases (62.74%) had placental abnormalities helpful to the etiology (parvovirus, syphilis, Turner's syndrome, etc.). In 20 instances, the clinical summary had no mention of either hydrops or any of the diseases leading to it. The autopsy in conjunction with placental examination and fetal ultrasound represent the best combination to determine the etiology of NIHF among stillborn fetuses.

Placental pathology in fetal bartter syndrome

Bartter syndrome, which presents clinically with polyuria, urinary potassium loss, hypokalemia, hypercalciuria, and alkalosis, is an autosomal recessive disorder with mutations in genes encoding the Na-K-2Cl cotransporter, the chloride channel CLC-NKB, and the potassium channel ROMK. Prenatal diagnosis of Bartter syndrome is now possible; however, there are no reports of the placental pathology associated with fetal Bartter syndrome. We present the placental pathologic findings in two siblings with fetal Bartter syndrome. Both pregnancies were complicated by polyhydramnios and preterm delivery. The first pregnancy delivered at 30 weeks, and Bartter syndrome was diagnosed in the perinatal period. The subsequent pregnancy required periodic therapeutic amniocentesis secondary to massive polyhydramnios and delivered at 32 weeks gestation. The suspicion of fetal Bartter syndrome was very high in this second pregnancy, and the infant was confirmed to have Bartter syndrome subsequently. Both placentas were large for gestational age, weighing greater than the 95th percentile. Microscopic examination showed extensive subtrophoblastic basement membrane mineralization (special stains positive for iron and calcium) in the chorionic villi. This striking finding was present in both placentas. Subtrophoblastic mineralization has been described in the literature in placentas of fetuses with abnormalities including anencephaly, trisomy 21, and other congenital abnormalities; however, it has also been described in normal pregnancies. Mechanisms of calcification in the placenta are not well understood, but these striking cases suggest that defects in fetal renal excretion of ions can lead to dystrophic calcification within the placenta, particularly in a subtrophoblastic pattern.