Meconium aspiration in the midtrimester fetus: an autopsy study

Colloidal iron staining used for amniotic fluid in lung sections of stillborn infants in histopathology

In forensic pathology, intrauterine amniotic fluid aspiration must be examined in lung sections of a stillborn fetus in late pregnancy. Alcian blue staining and immunohistochemistry are routinely performed using anti-cytokeratin antibody to detect the components. Colloidal iron staining is another method for acidic mucus polysaccharides. Retrospectively, we examined 15 forensic cases of stillborn and neonatal deaths with autopsies conducted at our department. Colloidal iron staining caused positive features of amniotic mucin in 14 cases, but Alcian blue staining could not be confirmed clearly in 8 cases because of weak color development. For detection of amniotic mucin, colloidal iron staining showed a richer color with contrast than other methods. Moreover, mucin masses were observed in two live-born infants, and in all stillborn infants, one of which was clinically diagnosed as having meconium aspiration syndrome. Non-specific reaction to iron ions such as hemosiderin-phagocytic macrophages might occur in the lung sections. However, colloidal iron staining should be the alternative routine for lung tissue from stillborn infants.

The fetal inflammatory response syndrome: the origins of a concept, pathophysiology, diagnosis, and obstetrical implications

The fetus can deploy a local or systemic inflammatory response when exposed to microorganisms or, alternatively, to non-infection-related stimuli (e.g., danger signals or alarmins). The term "Fetal Inflammatory Response Syndrome" (FIRS) was coined to describe a condition characterized by evidence of a systemic inflammatory response, frequently a result of the activation of the innate limb of the immune response. FIRS can be diagnosed by an increased concentration of umbilical cord plasma or serum acute phase reactants such as C-reactive protein or cytokines (e.g., interleukin-6). Pathologic evidence of a systemic fetal inflammatory response indicates the presence of funisitis or chorionic vasculitis. FIRS was first described in patients at risk for intraamniotic infection who presented preterm labor with intact membranes or preterm prelabor rupture of the membranes. However, FIRS can also be observed in patients with sterile intra-amniotic inflammation, alloimmunization (e.g., Rh disease), and active autoimmune disorders. Neonates born with FIRS have a higher rate of complications, such as early-onset neonatal sepsis, intraventricular hemorrhage, periventricular leukomalacia, and death, than those born without FIRS. Survivors are at risk for long-term sequelae that may include bronchopulmonary dysplasia, neurodevelopmental disorders, such as cerebral palsy, retinopathy of prematurity, and sensorineuronal hearing loss. Experimental FIRS can be induced by intra-amniotic administration of bacteria, microbial products (such as endotoxin), or inflammatory cytokines (such as interleukin-1), and animal models have provided important insights about the mechanisms responsible for multiple organ involvement and dysfunction. A systemic fetal inflammatory response is thought to be adaptive, but, on occasion, may become dysregulated whereby a fetal cytokine storm ensues and can lead to multiple organ dysfunction and even fetal death if delivery does not occur ("rescued by birth"). Thus, the onset of preterm labor in this context can be considered to have survival value. The evidence so far suggests that FIRS may compound the effects of immaturity and neonatal inflammation, thus increasing the risk of neonatal complications and long-term morbidity. Modulation of a dysregulated fetal inflammatory response by the administration of antimicrobial agents, anti-inflammatory agents, or cell-based therapy holds promise to reduce infant morbidity and mortality.

Meconium aspiration syndrome: Incidence and outcomes using discharge data

BACKGROUND

Meconium aspiration syndrome (MAS) is a leading cause of morbidity and mortality among term, otherwise healthy newborns, yet population studies are rare. Definitions, outcomes and International Classification of Diseases (ICD) codes are heterogenous, complicating estimates of incidence, outcomes and risks.

AIMS

To measure population incidence, risks and outcomes of MAS by ICD codes.

STUDY DESIGN

Retrospective population study.

SUBJECTS

Kids Inpatient Database (KID) 2012, a nationally representative weighted sample of newborn discharges in the United States.

OUTCOME MEASURES

Incidence, demographic distribution, and comorbidity associated with MAS.

RESULTS

In 2012 there were 9295 weighted discharges diagnosed MAS with symptoms (2.49/1000) and 4304 cases without symptoms (1.15/1000). Newborns with symptoms had nearly twice the length of stay (LOS) (6.68 vs 3.65 days, p 0.001) and nearly 3 times the total charges ($44,473 versus $15,461, p < 0.001) as those without symptoms. Incidence of death was over four times higher (7.7/1000 vs 1.7/1000, p < 0.001), persistent pulmonary hypertension 3 times higher (57.6/1000 vs 15.8/1000, p < 0.001), and hypoxic ischemic encephalopathy 5 times higher (6.2/1000 vs 1.2/1000, p < 0.001) among MAS cases with respiratory symptoms than MAS cases without respiratory symptoms. Odds ratio of MAS with symptoms was 1.54 (95% CI 1.39-1.73) for black newborns compared to whites.

CONCLUSIONS

Discharge data are useful for providing population estimates of MAS incidence. Prior studies have used consolidated ICD codes for MAS (with and without respiratory symptoms), yet these represent very different disease severities. Combining MAS diagnoses with and without respiratory symptoms misrepresents incidence and disease severity, complicating comparisons of outcomes and prevention strategies.

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

BACKGROUND

Meconium-stained amniotic fluid (MSAF) is a common occurrence among women in spontaneous labor at term, and has been associated with adverse outcomes in both mother and neonate. MSAF is a risk factor for microbial invasion of the amniotic cavity (MIAC) and preterm birth among women with preterm labor and intact membranes. We now report the frequency of MIAC and the presence of bacterial endotoxin in the amniotic fluid of patients with MSAF at term.

MATERIALS AND METHODS

We conducted a cross-sectional study including women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and were later determined to be at term (n = 108). Patients were allocated into two groups: (1) MSAF (n = 66) and (2) clear amniotic fluid (n = 42). The presence of bacteria was determined by microbiologic techniques, and endotoxin was detected using the Limulus amebocyte lysate (LAL) gel clot assay. Statistical analyses were performed to test for normality and bivariate comparisons.

RESULTS

Bacteria were more frequently present in patients with MSAF compared to those with clear amniotic fluid [19.6% (13/66) versus 4.7% (2/42); p < 0.05]. The microorganisms were Gram-negative rods (n = 7), Ureaplasma urealyticum (n = 4), Gram-positive rods (n = 2) and Mycoplasma hominis (n = 1). The LAL gel clot assay was positive in 46.9% (31/66) of patients with MSAF, and in 4.7% (2/42) of those with clear amniotic fluid (p < 0.001). After heat treatment, the frequency of a positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) versus 2.3% (1/42), p < 0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher [1.3 (0.7-1.9) versus 0.6 (0.3-1.2), p = 0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) versus 9 (7.4-12.6), p < 0.001] in the MSAF group, than in those with clear amniotic fluid.

CONCLUSION

MSAF at term was associated with an increased incidence of MIAC. The index of suspicion for an infection-related process in postpartum women and their neonates should be increased in the presence of MSAF.