Haemosiderosis in the placenta does not appear to be related to chronic placental separation or adverse neonatal outcome

Meconium-stained amniotic fluid

Green-stained amniotic fluid, often referred to as meconium-stained amniotic fluid, is present in 5% to 20% of patients in labor and is considered an obstetric hazard. The condition has been attributed to the passage of fetal colonic content (meconium), intraamniotic bleeding with the presence of heme catabolic products, or both. The frequency of green-stained amniotic fluid increases as a function of gestational age, reaching approximately 27% in post-term gestation. Green-stained amniotic fluid during labor has been associated with fetal acidemia (umbilical artery pH <7.00), neonatal respiratory distress, and seizures as well as cerebral palsy. Hypoxia is widely considered a mechanism responsible for fetal defecation and meconium-stained amniotic fluid; however, most fetuses with meconium-stained amniotic fluid do not have fetal acidemia. Intraamniotic infection/inflammation has emerged as an important factor in meconium-stained amniotic fluid in term and preterm gestations, as patients with these conditions have a higher rate of clinical chorioamnionitis and neonatal sepsis. The precise mechanisms linking intraamniotic inflammation to green-stained amniotic fluid have not been determined, but the effects of oxidative stress in heme catabolism have been implicated. Two randomized clinical trials suggest that antibiotic administration decreases the rate of clinical chorioamnionitis in patients with meconium-stained amniotic fluid. A serious complication of meconium-stained amniotic fluid is meconium aspiration syndrome. This condition develops in 5% of cases presenting with meconium-stained amniotic fluid and is a severe complication typical of term newborns. Meconium aspiration syndrome is attributed to the mechanical and chemical effects of aspirated meconium coupled with local and systemic fetal inflammation. Routine naso/oropharyngeal suctioning and tracheal intubation in cases of meconium-stained amniotic fluid have not been shown to be beneficial and are no longer recommended in obstetrical practice. A systematic review of randomized controlled trials suggested that amnioinfusion may decrease the rate of meconium aspiration syndrome. Histologic examination of the fetal membranes for meconium has been invoked in medical legal litigation to time the occurrence of fetal injury. However, inferences have been largely based on the results of in vitro experiments, and extrapolation of such findings to the clinical setting warrants caution. Fetal defecation throughout gestation appears to be a physiologic phenomenon based on ultrasound as well as in observations in animals.

Histological distribution pattern of hemosiderin deposition on the chorionic plate and fetal membrane of diffuse chorioamniotic hemosiderosis related to chronic abruption oligohydramnios sequence

INTRODUCTION

Chronic abruption oligohydramnios sequence (CAOS) is histologically characterized by diffuse chorioamniotic hemosiderosis (DCH). However, the criteria for the histological evaluation of the extent of CAOS-related hemosiderin deposition (HD) of the membranes and the difference in HD between the chorionic plate (CP) and fetal membrane (FM) are not well studied. This case control study compared the degree and distribution pattern of HD on CP and FM to present the histological features of DCH and the criteria for histological evaluation.

METHODS

From the medical records of Kyoto University Hospital (2010-2019), we selected 20 CAOS cases that were clinically diagnosed by Elliot's criteria. Twenty non-CAOS cases matched to the CAOS group by gestational age were selected as controls. We compared the clinical data and pathological features in the two groups. We performed iron staining in all the cases and analyzed HD in CP and FM according to the histological score (H-Score: 0-12), which was determined as the density (0-3) multiplied by the extent of staining (0-4).

RESULTS

HD was found in 100% (20/20) of CAOS and 15% (3/20) of control cases. In both the FM and CP, CAOS cases showed a significantly higher HS than control cases (CAOS, HS = 4-12; Control, HS = 0-1, p < 0.0001). Three CAOS patients presented HD alone in the CP. The HS of the CP was significantly higher than that of the FM (p = 0.0003).

DISCUSSION

CAOS presented DCH with HS ≥ 4. This study showed that the CP might be more suitable for evaluating DCH than the FM.

Amniotic membrane and placental histopathological findings after open and fetoscopic prenatal neural tube defect repair

OBJECTIVES

To describe and compare placental and amniotic histology in women who underwent a fetoscopic myelomeningocele repair to those who underwent an open hysterotomy myelomeningocele repair. Also, we intended to compare findings from both prenatal repair groups to age-matched control pregnant patients.

METHODS

Placental and membrane histopathology from 43 prenatally repaired spina bifida cases (17 fetoscopic and 26 open) and 18 healthy controls were retrospectively assessed. Quantitative assessment of histopathology included apoptosis count and maternal and fetal underperfusion scores. Qualitative assessment included the detection of pigmented macrophages and/or signs of placental/amniotic inflammation. Associations between the duration of surgery or the duration of CO₂ insufflation and quantitative histological parameters were tested.

RESULTS

Fetoscopic surgery cases did not show significant differences in any of the studied parameters when compared against controls. No differences were detected either when compared with open repaired cases, except for lower proportion of pigmented laden macrophages in the fetoscopic group (11.8% vs 61.5%, P < 0.01). No associations between the duration of surgery or the duration of CO₂ exposure and any of the quantitative histological parameters were detected.

CONCLUSIONS

These preliminary results support the lack of detrimental effects of the use of heated and humidified CO₂ gas for uterine insufflation to fetal membranes and placenta.

Hypoxic patterns of placental injury: a review

CONTEXT

In utero hypoxia is an important cause of perinatal morbidity and mortality and can be evaluated retrospectively to explain perinatal outcomes, to assess recurrence risk in subsequent pregnancies, and to investigate for medicolegal purposes by identification of many hypoxic placental lesions. Definitions of some placental hypoxic lesions have been applied relatively liberally, and many of them are frequently underreported. Objectives To present a comprehensive assessment of the criteria for diagnosing acute and chronic histologic features, patterns, and lesions of placental and fetal hypoxia and to discuss clinicopathologic associations and limitations of the use thereof. The significance of lesions that have been described relatively recently and are not yet widely used, such as laminar necrosis; excessive, extravillous trophoblasts; decidual multinucleate extravillous trophoblasts; and, most important, the patterns of diffuse chronic hypoxic preuterine, uterine, and postuterine placental injury and placental maturation defect, will be discussed.

DATA SOURCES

Literature review.

CONCLUSIONS

The placenta does not respond in a single way to hypoxia, and various placental hypoxic features should be explained within a clinical context. Because the placenta has a large reserve capacity, hypoxic lesions may not result in poor fetal condition or outcome. On the other hand, very acute, in utero, hypoxic events, followed by prompt delivery, may not be associated with placental pathology, and many poor perinatal outcomes can be explained by an etiology other than hypoxia. Nevertheless, assessment of placental hypoxic lesions is helpful for retrospective explanations of complications in pregnancy and in medicolegal investigation.

Ovine uterine space restriction alters placental transferrin receptor and fetal iron status during late pregnancy

BACKGROUND

Fetal growth restriction is reported to be associated with impaired placental iron transport. Transferrin receptor (TfR) is a major placental iron transporter in humans but has not been studied in sheep. TfR is regulated by both iron and nitric oxide (NO), the molecule produced by endothelial nitric oxide synthase (eNOS). We hypothesized that limited placental development downregulates both placental TfR and eNOS expression, thereby lowering fetal tissue iron.

METHODS

An ovine surgical uterine space restriction (USR) model, combined with multifetal gestation, tested the extremes of uterine and placental adaptation. Blood, tissues, and placentomes from non-space restricted (NSR) singletons were compared with USR fetuses at gestational day (GD) 120 or 130.

RESULTS

When expressed proportionate to fetal weight, liver iron content did not differ, whereas renal iron was higher in USR vs. NSR fetuses. Renal TfR protein expression did not differ, but placental TfR expression was lower in USR fetuses at GD130. Placental levels of TfR correlated to eNOS. TfR was localized throughout the placentome, including the hemophagous zone, implicating a role for TfR in ovine placental iron transport.

CONCLUSION

Fetal iron was regulated in an organ-specific manner. In USR fetuses, NO-mediated placental adaptations may prevent the normal upregulation of placental TfR at GD130.