| Summary: | Particulate matter with a diameter less than 2.5 µm (PM<sub>2.5</sub>) and its chemical constituents—including ammonium (NH<sub>4</sub><sup>+</sup>), sulfate (SO<sub>4</sub><sup>2−</sup>), nitrate (NO<sub>3</sub><sup>−</sup>), organic carbon (OC), soil dust, and black carbon (BC)—have been increasingly recognized for their potential impact on fetal neurodevelopment. This systematic review aimed to synthesize current evidence on the relationship between prenatal exposure to PM<sub>2.5</sub> and its chemical components and neurodevelopmental outcomes in neonates, focusing on diagnoses such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Following PRISMA 2020 guidelines, a comprehensive literature search was conducted on PubMed and Embase databases from April to July 2025. Twenty-five studies meeting inclusion criteria were analyzed, of which sixteen addressed PM<sub>2.5</sub> exposure generally, and nine assessed specific chemical constituents. The findings indicate that increased exposure to PM<sub>2.5</sub>, particularly during the third trimester, is associated with a higher risk of ASD. Additionally, prenatal exposure may adversely affect early neurodevelopmental domains including motor skills, problem-solving, and social interactions. Certain PM<sub>2.5</sub> components, notably sulfate ions (SO<sub>4</sub><sup>2−</sup>), were identified as important contributors to neurological health outcomes. These results underscore the importance of reducing prenatal exposure to PM<sub>2.5</sub> and its harmful constituents to protect neurodevelopment.
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