This prospective cohort study aims to investigate the impact of early antibiotic exposure on the establishment of gut microbiota and motility in newborns, particularly preterm infants. The study will explore the correlation between antibiotic exposure, gut microbiota colonization, and 5-hydroxytryptamine (5-HT) levels, which are critical for gastrointestinal motility. The findings may provide insights into optimizing antibiotic use and improving gastrointestinal health in neonates.

Inclusion Criteria:

• Newborns admitted within 72 hours of birth
• Gestational age 24-36 weeks (preterm) and term infants
• Informed consent obtained from parents or guardian

Exclusion Criteria:

• Congenital gastrointestinal malformations (e.g., intestinal atresia, Hirschsprung's disease)
• Severe systemic or organ-specific diseases
• Expected mortality due to severe illness

This study will enroll newborns admitted to the neonatal unit of Jilin University First Hospital from November 2024 to November 2027.