Greater severity of meconium stained amniotic fluid associated with increased maternal infectious morbidity: Study
Meconium-stained amniotic fuid (MSAF) is observed in 5% to 20% of laboring patients, with the incidence reaching approximately 27% in post-term pregnancies. The presence of meconium in the amniotic fluid has been linked to fetal acidemia, hypoxia, and hypoxic-ischemic encephalopathy, meconium aspiration syndrome, seizures, and neonatal mortality. The relationship between MSAF and clinical chorioamnionitis, as well as neonatal sepsis, has been documented, yet the precise mechanisms remain unclear. Additionally, the correlation between prolonged labor and MSAF was described in the past.
In women with prolonged rupture of membranes (ROM) and intrapartum fever (IPF), MSAF increased the risk of isolating Enterobacteriaceae from chorioamnionitic swabs. In a study examining the impact of MSAF on bacterial growth in amniotic fluid, it was observed that even low concentrations of meconium (up to 1.5 mg/ml) inhibited the growth of Escherichia coli. In light of these conflicting findings, a study aimed to explore the relationship between the thickness of MSAF and the risk of maternal infectious morbidity. Additionally, authors aimed to assess the distribution of pathogens in chorioamnionitic swab cultures relative to the varying degrees of MSAF thickness.
A retrospective study was carried out of 15,950 term singleton pregnancies at a tertiary hospital (2020–2024). Women were categorized into four groups based on the presence and thickness of MSAF: clear, light, intermediate, and thick. The co-primary outcomes were clinical chorioamnionitis and puerperal endometritis, defined as a composite maternal infectious morbidity. In women with intrapartum fever (IPF), chorioamniotic swabs were obtained and compared according MSAF thickness. Multivariate analysis identified predictors of a composite maternal infections and adverse neonatal outcomes.
Of the cohort, 13,745 had clear amniotic fluid, and 2,205 had MSAF (561 light, 1,426 intermediate, 218 thick). The incidence of maternal infections increased with MSAF thickness, with thick MSAF showing the highest rates of clinical chorioamnionitis (4.1%, p< 0.001) and endometritis (1.4%, p=0.039). In IPF cases, thicker MSAF was associated with a higher prevalence of positive swab cultures, particularly of Enterobacteriaceae (61.9%). Group B Streptococcus (GBS) remained consistent across all MSAF groups. Multivariate analysis showed that MSAF levels were associated with increased maternal infectious morbidity (p< 0.001). Additional risk factors for maternal infections included nulliparity (p< 0.001), catheter balloon insertion (p=0.004), prolonged ROM (p< 0.001), and cesarean delivery (p< 0.001). In contrast, only intermediate (p< 0.001) and thick MSAF (p< 0.001) correlated with adverse neonatal outcomes.
The rates of clinical chorioamnionitis and puerperal endometritis were observed to increase proportionally with the severity of MSAF. In women with intrapartum fever, thicker MSAF was associated with a higher prevalence of Enterobacteriaceae in chorioamnionitic swabs, though GBS isolation rates remained consistent. Multivariate analysis demonstrated that all MSAF degrees were associated with an increased risk of maternal infectious morbidity. Additional risk factors for maternal infections identified in the analysis included nulliparity, catheter balloon insertion, prolonged ROM duration, and CD. In contrast, only intermediate and thick MSAF correlated with adverse neonatal outcomes, while light MSAF did not show the same association.
Increasing severity of MSAF was associated with maternal infectious morbidity and particularly Enterobacteriaceae related infections. This underlines the importance of close monitoring and the potential need for preventive measures in cases where thick MSAF is present. Studies about preventive measures in cases of thick MSAF are warranted.
Source: Raneen Abu Shqara, Lior Lowenstein, Maya Frank Wolf; Archives of Gynecology and Obstetrics https://doi.org/10.1007/s00404-024-07808-4
