OBJECTIVE: To determine the association between antibiotic exposure following birth and necrotizing enterocolitis (NEC) severity in preterm infants. METHODS: This single center matched case-control study included infants with NEC (n=107) and matched controls (n= 130) with antibiotic exposure =<
3 days and >
3 days after birth. RESULTS: Out of 212 infants,103 infants (48.5%) received antibiotics =<
3 days, and 109 infants (51.5%) received antibiotics >
3 days. On the multivariate regression, Infants receiving antibiotics for >
3 day had higher risk for medical NEC (aOR 2.61,95% CI 1.35 -5.16
p=0.005) and surgical NEC (aOR 3.33, CI 1.57-7.40
p=0.02) than controls. In NEC cohort, those receiving antibiotics for >
3 days were like to die (OR 7.88,95% CI 1.99- 53.74
p=0.010) than those receiving antibiotics <
3 days. CONCLUSION: Infants exposed with early antibiotics >
3 days after birth were more likely associated with NEC and were at greater risk of death.