Objective To investigate the association of histological chorioamnionitis (HCA) and meconium-stained amniotic fluid (MSAF) with adverse pregnancy outcomes in neonates. Methods Neonates and their mothers who delivered from May 2021 to January 2024 in the department of neonatology in a hospital were selected as the research subjects. According to placenta pathological diagnosis, participants were divided into the HCA group and the non-HCA group. Clinical data, MSAF incidence, and adverse pregnancy outcomes among neonates with different MSAF levels were compared between two groups. The relationship between HCA and adverse pregnancy outcomes in neonates with different MSAF severity levels was analyzed using logistic regression analysis model, and the impact of the interaction between HCA and MSAF on adverse pregnancy outcomes in neonates was evaluated. Results A total of 300 neonates and their mothers were included in the analysis, with 113 in the HCA group and 187 in the non-HCA group. There was a statistical difference in the occurrence of MSAF with different severity between two groups of neonates (χ²=25.39, P<0.05). The incidence of HCA increased with the increased severity of MSAF. The incidences of neonatal pneumonia, intraventricular hemorrhage, early-onset septicemia and bronchopulmonary dysplasia were all statistically different under different MSAF levels (all P<0.05). As MSAF severity increased, the risk of neonates developing the above-mentioned diseases also increased gradually. HCA was found to be independently associated with neonatal pneumonia, intraventricular hemorrhage, early-onset sepsis, and bronchopulmonary dysplasia under different MSAF levels. Interaction analysis revealed that when HCA and MSAF co-occurred, there was a remarkable increase in the risk of adverse pregnancy outcomes in neonates (OR=6.30; 95%CI: 2.53-10.20). Conclusion MSAF and HCA are both independent risk factors for adverse pregnancy outcomes in neonates, and the coexistence of MSAF and HCA significantly increases this risk.