Association of Meconium-Stained Amniotic Fluid and Histological Chorioamnionitis with Fetal Inflammatory Response in Preterm Deliveries.

Background: The importance and etiology of meconium-stained amniotic fluid (MSAF) in preterm pregnancies are still poorly understood. Among other factors, intrauterine inflammation is proposed to be a pathophysiological change associated with MSAF. To study the extent of intrauterine inflammation, histological evaluation represents the "gold standard" of diagnostics.

Objective: To investigate the concomitant occurrence of MSAF and histological chorioamnionitis (HCA) and fetal inflammatory response (FIR). To investigate the incidence of short-term neonatal outcomes in preterm infants born from MSAF.

Methods: We conducted a single-center retrospective study in a tertiary neonatal intensive care unit between 2020 and 2022. 237 preterm infants born ≤ 32 weeks or with ≤1500 g birthweight were investigated. The group of infants born from MSAF was compared to the group of infants born from clear amniotic fluid (CAF). The variables measured were the following: HCA, FIR, maternal and fetal vascular malformations (MVM, FVM), maternal clinical and laboratory signs of chorioamnionitis (CA), early neonatal outcomes, neonatal white blood cell count (WBC) in the first day of life, and neonatal c-reactive protein (CRP) level on the second day of life. Histological evaluation of the placenta and the umbilical cord was based on the recommendation of the 2014 Amsterdam Placental Workshop Group Consensus Statement (APWGCS).

Results: Out of 237 preterm infants (mean gestational age: 28.6 (95% CI: 28.2; 28.9) weeks, mean birth weight: 1165 (95% CI: 1110; 1218) grams), 22 were born from MSAF. There was no difference between the perinatal characteristics of the two groups. A higher incidence of HCA (54.5% vs. 32.6%; p: <0.001), a higher incidence of stage 3 HCA (45.4% vs. 9.3%), a higher incidence of FIR (50% vs. 16.7%; p: <0.001), and a higher incidence of stage 3 FIR (18.2% vs. 1.9%) were found in the MSAF group in comparison with the CAF group. A higher incidence of elevated (>30 mg/L) maternal CRP level (36.8% vs. 15.3%; p: 0.02) and elevated (>15 mg/L) neonatal CRP level (31.8% vs. 14.4%; p: 0.03) was detected in the MSAF group. Among neonatal complications, severe (Stage III/IV) intraventricular hemorrhage (IVH) had a higher incidence in the MSAF group (22.2% vs. 5.1%; p: 0.005).

Conclusions: MSAF in preterm pregnancies is associated with a severe maternal and fetal inflammatory response in the placenta and the umbilical cord. MSAF is also accompanied by elevated systemic inflammatory parameters and a higher incidence of severe neonatal IVH as well.