Background: Systematic reviews of randomised controlled trials report that probiotics reduce the risk of necrotising enterocolitis (NEC) in preterm neonates.

Aim: To determine whether routine probiotic supplementation (RPS) to preterm neonates would reduce the incidence of NEC.

Methods: The incidence of NEC ≥ Stage II and all-cause mortality was compared for an equal period of 24 months 'before' (Epoch 1) and 'after' (Epoch 2) RPS with Bifidobacterium breve M-16V in neonates <34 weeks. Multivariate logistic regression analysis was conducted to adjust for relevant confounders.

Results: A total of 1755 neonates (Epoch I vs. II: 835 vs. 920) with comparable gestation and birth weights were admitted. There was a significant reduction in NEC ≥ Stage II: 3% vs. 1%, adjusted odds ratio (aOR) = 0.43 (95%CI: 0.21-0.87); 'NEC ≥ Stage II or all-cause mortality': 9% vs. 5%, aOR = 0.53 (95%CI: 0.32-0.88); but not all-cause mortality alone: 7% vs. 4%, aOR = 0.58 (95% CI: 0.31-1.06) in Epoch II. The benefits in neonates <28 weeks did not reach statistical significance: NEC ≥ Stage II: 6% vs. 3%, aOR 0.51 (95%CI: 0.20-1.27), 'NEC ≥ Stage II or all-cause mortality', 21% vs. 14%, aOR = 0.59 (95%CI: 0.29-1.18); all-cause mortality: 17% vs. 11%, aOR = 0.63 (95%CI: 0.28-1.41). There was no probiotic sepsis.

Conclusion: RPS with Bifidobacterium breve M-16V was associated with decreased NEC≥ Stage II and 'NEC≥ Stage II or all-cause mortality' in neonates <34 weeks. Large sample size is required to assess the potential benefits of RPS in neonates <28 weeks.