Risk factors differentiating mild/moderate from severe meconium aspiration syndrome in meconium-stained neonates

Impact of perinatal factors on meconium aspiration syndrome in full-term newborns and the construction of a column chart prediction model: An observational study

To explore the influence of perinatal-related factors on meconium aspiration syndrome (MAS) in full-term neonates and construct a nomogram prediction model for risk stratification of neonatal MAS and adoption of preventive measures. A total of 424 newborns and their mothers who were regularly examined at our hospital between January 2020 and December 2023 who had meconium-contaminated amniotic fluid during delivery were retrospectively selected as participants. Neonates were divided into MAS and non-MAS groups based on whether MAS occurred within 3 days after birth. Data from the 2 groups were analyzed, and factors influencing MAS were screened using multivariate logistic regression analysis. The R3.4.3 software was used to construct a nomogram prediction model for neonatal MAS risk. Receiver operating characteristic (ROC) curve analysis and the Hosmer-Lemeshow goodness-of-fit test were used to evaluate the performance of the model, and its clinical effectiveness was evaluated using a decision curve. Among the 424 neonates with meconium-stained amniotic fluid, 51 developed MAS within 3 days of birth (12.03%). Multivariate logistic regression analysis showed that a low amniotic fluid index before delivery (OR = 2.862, P = .019), advanced gestational age (OR = 0.526, P = .034), cesarean section (OR = 2.650, P = .013), severe amniotic fluid contamination (OR = 4.199, P = .002), low umbilical cord blood pH (OR = 2.938, P = .011), and low neonatal Apgar 1-min score (OR = 3.133, P = .006) were influencing factors of MAS in full-term neonates. Based on the above indicators, a nomogram prediction model for MAS risk of full-term newborns was constructed. The area under the ROC curve of the model was 0.931. The model was also tested for goodness-of-fit deviation (χ2 = 3.465, P = .903). Decision curve analysis found that the model was clinically effective in predicting the net benefit of MAS risk in neonates with meconium-stained amniotic fluid. The construction of a column chart prediction model for neonatal MAS risk based on prenatal amniotic fluid index, gestational age, delivery method, amniotic fluid contamination level, newborn umbilical blood pH value, and Apgar 1-min score has a certain application value.

Clinical characteristics of meconium aspiration syndrome in neonates with different gestational ages and the risk factors for neurological injury and death: A 9-year cohort study

Background

The presence of meconium is associated with gestational age, and the incidence of meconium aspiration syndrome (MAS) increases with gestational age. Our study compared the differences in the clinical characteristics of patients with MAS at different gestational ages and discussed the risk factors for neurological injury and death from MAS.

Methods

A total of 294 neonates diagnosed with MAS between 2013 and 2021 were included. Patients were divided into preterm, early-term, full-term, and late-term groups according to gestational age. We compared the patients' basic demographic, treatment, complications, and clinical outcomes in the different groups. We also analyzed the risk factors of neurological injury and death in patients with MAS.

Results

The mean age at admission (0.55 ± 0.9 h) was lower and the proportion of cesarean deliveries (90.00%, 27/30) was higher in the preterm group than in the other three groups. There was no statistically significant difference among the four groups regarding 1- and 5-min Apgar scores and the need for delivery room resuscitation. In terms of complications, early-term infants had the highest incidence of neurological injury (52.9%, 27/51), and late-term infants had the highest incidence of pneumothorax (37.8%, 17/45). The overall mortality rate of children with MAS was 7.80% (23/294), and the difference in mortality rates among the four groups was not significant. Low 1-min Apgar score and gestational age, metabolic acidosis, and respiratory failure were independent risk factors for neurological injury; metabolic acidosis, respiratory failure, and sepsis were independent risk factors for death in neonates with MAS.

Conclusion

The clinical characteristics of MAS neonates of different gestational age are different mainly in complications. Early-term infants are more likely to complicate with neurological injury, and late-term infants are more likely to complicate with pneumothorax. Low 1-min Apgar score and gestational age, metabolic acidosis, and respiratory failure were established as risk factors for neurological injury; metabolic acidosis, respiratory failure, and sepsis were independent risk factors for death in neonates with MAS.

Epidemiology and risk factors for acquiring and predicting disease severity in meconium aspiration syndrome

Background. Meconium aspiration syndrome (MAS) occurs in approximately 5% of babies born through meconium-stained amniotic fluid. Risk factors associated with severity of MAS in neonates from developing countries has been infrequently described.  Objective. To identify incidence and risk factors associated with the severity of MAS in a lower middle-income country.  Method. A retrospective descriptive analysis was conducted on records of neonates diagnosed with MAS at four regional hospitals in the eThekwini district of KwaZulu-Natal, South Africa, between 1 January 2015 and 31 December 2017.  Results. A total of 187 neonates had been diagnosed with MAS, of whom 157 survived. The overall incidence of MAS was 2 per 1 000 live births. All the neonates were born through thick meconium. The majority (n=119, 63.6%) of patients were male. Asphyxia was documented in 97 cases (51.9%) and was significantly associated with severe disease (p<0.001). Seizures were noted in 91patients (48.7%), of which 86 (94.5%) occurred in neonates with asphyxia. A quarter of the sample (n=47, 25%) were outborn, with severe disease associated significantly with this group (p=0.025). Multiple logistic regression showed that the occurrence of seizures was significantly associated with severe MAS, (adjusted odds ratio = 23.7, 95% confidence interval 7.58 - 97.7; p<0.001).  Conclusion. Neonates born through thick meconium, with moderate to severe asphyxia that is associated with seizures are at increased risk of developing severe MAS. Close monitoring of labour in the intrapartum period, early recognition of fetal distress and timely obstetric intervention are crucial to prevent asphyxia. 

The clinical effects of high-frequency oscillatory ventilation in the treatment of neonatal severe meconium aspiration syndrome complicated with severe acute respiratory distress syndrome

OBJECTIVE

To explore the efficacy and safety of high-frequency oscillatory ventilation (HFOV) in the treatment of severe meconium aspiration syndrome (MAS) complicated with severe acute respiratory distress syndrome (ARDS).

METHODS

A total of 65 infants with severe MAS complicated with severe ARDS were included in the study. The clinical efficacy of treatment for the HFOV group (n = 31) and the conventional mechanical ventilation (CMV) group (n = 34) was retrospectively analysed. The partial pressure of oxygen (PaO₂), partial pressure of carbon dioxide (PaCO₂), PaO₂/fraction of inspired oxygen (FiO₂), and oxygen index values before and at 6, 12, 24, 48, and 72 h after mechanical ventilation, the mechanical ventilation time, oxygen inhalation time, incidence of complications, and outcomes of the two groups were compared.

RESULTS

At 6, 12, 24, and 48 h after mechanical ventilation, the PaO₂ in the HFOV group was significantly higher than in the CMV group, while the PaCO₂ in the HFOV group was significantly lower than in the CMV group (P < 0.05). At 6, 12, 24, 48, and 72 h after mechanical ventilation, PaO₂/FiO2 in the HFOV group was significantly higher than in the CMV group, and the OI in the HFOV group was significantly lower than in the CMV group (P < 0.05). Mechanical ventilation time, oxygen inhalation time, and the incidence of air leakage were significantly lower in the HFOV than in the CMV group (P < 0.05).

CONCLUSIONS

Overall, HFOV can effectively improve lung ventilation and oxygenation function, shorten ventilator treatment time, and reduce the incidence rate of air leakage for neonatal MAS, making it a safe and effective treatment option.

Prediction of meconium aspiration syndrome by data available before delivery

OBJECTIVE

To identify risk factors associated with the occurrence of meconium aspiration syndrome (MAS) among neonates.

METHODS

A retrospective case-control study in a university affiliated tertiary medical center, including all neonates born with meconium stained amniotic fluid (MSAF) between March 2011 and March 2020. Patients were categorized by the occurrence of MAS. Demographic, pregnancy and delivery characteristics were compared between the two groups. Risk factors for MAS were analyzed.

RESULTS

Of 90 579 singleton deliveries, a total of 11 856 with MSAF were included. Of these newborns, 78 (0.66%) were diagnosed with MAS Four factors were independently associated with MAS: delivery at <38 0/7 weeks (aOR [95% CI]: 3.48 (1.02-11.84), P = 0.046); higher body mass index (aOR [95% CI]: 1.09 (1.02-1.16), P = 0.003); lower amniotic fluid index (aOR [95% CI]: 0.99 (0.98-0.99), P = 0.032); higher white blood cell count (aOR [95% CI]: 1.11 (1.02-1.20), P = 0.009). The presence of one, two and three of the above-mentioned risk factors yielded a risk for MAS of 0.8%, 2.5% and 100%, respectively.

CONCLUSION

We identified independent risk factors for MAS and developed a risk score calculator. This tool may assist physicians in the management of deliveries complicated by MSAF.

Meconium Aspiration Syndrome: A Narrative Review

Meconium aspiration syndrome is a clinical condition characterized by respiratory failure occurring in neonates born through meconium-stained amniotic fluid. Worldwide, the incidence has declined in developed countries thanks to improved obstetric practices and perinatal care while challenges persist in developing countries. Despite the improved survival rate over the last decades, long-term morbidity among survivors remains a major concern. Since the 1960s, relevant changes have occurred in the perinatal and postnatal management of such patients but the most appropriate approach is still a matter of debate. This review offers an updated overview of the epidemiology, etiopathogenesis, diagnosis, management and prognosis of infants with meconium aspiration syndrome.

Outcomes of endotracheal suctioning in non-vigorous neonates born through meconium-stained amniotic fluid: a systematic review and meta-analysis

OBJECTIVE

We aimed to systematically review and analyse the outcomes of non-endotracheal suctioning (non-ETS) versus ETS in non-vigorous meconium-stained neonates.

DESIGN

We conducted a systematic review of non-ETS and ETS in non-vigorous infants born through meconium-stained amniotic fluid (MSAF). We searched PubMed/Medline, Scopus, Clinical Trials.gov, Cumulative Index to Nursing and Allied Health, and Cochrane Library databases from inception to November 2019, using keywords and related terms. Only non-vigorous infants born through MSAF included in randomised controlled trials, were included. We calculated overall relative risks (RRs) and mean differences with 95% CIs using a random-effects model, to determine the impact of ETS in non-vigorous infants born through MSAF.

MAIN OUTCOME MEASURES

The primary outcome was the incidence of meconium aspiration syndrome (MAS). Secondary outcomes were respiratory outcome measures (pneumothorax, persistent pulmonary hypertension of the newborn, secondary pneumonia, need for respiratory support, duration of mechanical ventilation), initial resuscitation and others including shock, perinatal asphyxia, convulsions, neonatal mortality, blood culture-positive sepsis and duration of hospital stay.

RESULTS

A total of 2085 articles were identified in the initial database search. Four studies, including 581 non-vigorous meconium-stained infants, fulfilled the inclusion criteria, comprising 292 infants in the non-ETS group and 289 in the ETS group. No statistically significant difference was found for MAS (RR 0.98; 95% CI 0.71 to 1.35).

CONCLUSIONS

Initiating ETS soon after birth in non-vigorous meconium-stained infants may not alter their neonatal outcomes.

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.

Influence of foetal inflammation on the development of meconium aspiration syndrome in term neonates with meconium-stained amniotic fluid

Background

Meconium-stained amniotic fluid is observed in approximately 10–15% of all deliveries; however, only 5% of neonates with meconium-stained amniotic fluid develop meconium aspiration syndrome (MAS). Although foetal distress and subsequent sympathetic stimulation have been considered as the primary upstream events of MAS, this clinical complication sometimes occurs due to other pathologies, such as intraamniotic inflammation. The aim of this study was to investigate whether the incidence of MAS is associated with the presence of funisitis and chorioamnionitis in term neonates with meconium-stained amniotic fluid.

Methods

Between April 2013 and March 2015, a total of 95 term neonates with meconium-stained amniotic fluid, who were hospitalized at a neonatal intensive care unit, were enrolled in the study. The placenta and umbilical cord were histopathologically examined. Clinical variables and histopathological findings associated with the incidence of MAS were studied.

Results

A total of 36 neonates developed MAS. Univariate logistic regression analysis revealed that a heavier birth weight, male sex, 1-min Apgar score ≤ 7, funisitis (but not chorioamnionitis), and elevated acute-phase inflammatory reaction score were associated with increased incidence of MAS (all p < 0.05). The multivariate model comprised funisitis (OR = 5.03, 95% CI [1.63–15.5], 1-min Apgar score ≤ 7 (OR = 2.74, 95% CI [1.06–7.09], and male sex (OR = 3.4, 95% CI [1.24–9.34].

Conclusion

In neonates with meconium-stained amniotic fluid, funisitis, as well as low 1-min Apgar score and male sex, was identified as an independent variable for MAS development. Intraamniotic inflammation might be involved in the pathological mechanisms of MAS.

The effect of meconium exposure on the expression and differentiation of amniotic fluid mesenchymal stem cells

BACKGROUND:

The goal of this study was to determine if exposure to meconium would alter the phenotype of amniotic fluid mesenchymal stem cells (AF-MSCs) and the ability of these cells to be differentiated into distal airway type cells.

METHODS:

Meconium was collected, lyophilized and resuspended in PBS at 3 different concentrations (high, medium, and low). AF-MSCs were cultured in the presence of this meconium suspension for 8 hours and then analyzed for changes in gene expression. Additionally, AF-MSCs exposed to meconium were differentiated for 14 days using modified small airway growth medium (mSAGM) and gene expression was determined. As a spontaneous differentiation control, meconium exposed AF-MSCs were cultured in amniotic fluid stem cell medium (AF medium).

RESULTS:

After 8 hours of exposure in culture, AF-MSCs had increased expression of distal airway genes aquaporin 5 (AQP5) and surfactant protein c (SPC) when cultured in AF medium containing meconium. These gene expression levels were similar to that of AF-MSCs that were differentiated in mSAGM for 14 days. Furthermore, there was an up regulation of pluripotency genes NANOG and OCT4 in response to low meconium concentration for 8 hours. Following 14 days of culture in mSAGM, there was an upregulation of TTF1, SPC and AQP5 expression in the control, as well as in the low and medium meconium exposed groups indicating that these cells were still able to be differentiated. High meconium concentration did, however, appear to influence the level of distal airway gene expression after 14 days in mSAGM. After 14 days in AF medium, there was significant downregulation in pluripotency and mesenchymal markers as well as distal airway gene expression in all groups.

CONCLUSION:

The phenotype of AF-MSCs is modulated by meconium exposure; however, the cells were still able to differentiate into distal airway gene and protein expression. This result supports the hypothesis that progenitor cells exist in the amniotic fluid and the presence of meconium may affect their initial phenotype. However, these cells were still able to be differentiated to a distal lung phenotype.

Meconium aspiration syndrome: risk factors and predictors of severity

PURPOSE

To identify risk factors and predictors of severity associated with meconium aspiration syndrome (MAS) in the patients admitted to the neonatal intensive care unit (NICU).

MATERIALS AND METHODS

Retrospective study including newborns admitted, between 2005 and 2015, with a diagnosis of MAS.

RESULTS

Of the newborns admitted to the NICU, 0.66% were diagnosed with MAS. These had higher prevalence of caesarean delivery (p < .001), nonreassuring or abnormal cardiotocography (CTG) (p < .001), intrapartum maternal fever (p = .002), Apgar scores at the first minute <7 (p < .001) and need of endotracheal intubation at birth (p < .001). Newborns with severe MAS had higher median reactive C protein (86.9 versus 9.65, p = .001) and 73.3% had pulmonary hypertension (p = .027). They required significantly more days of oxygen therapy, mechanical ventilation, nitric oxide, inotropic, and surfactant therapy, as well as longer hospital stay.

CONCLUSIONS

Nonreassuring or abnormal CTG and low Apgar score at the first minute were established as risk factors for MAS and need of surfactant therapy as a predictor of severity.

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.