Sam J Oddie, Lauren Young, William McGuire

Early enteral feeding practices are potentially modifiable risk factors for necrotising enterocolitis (NEC) in very preterm or very low birth weight (VLBW) infants. Observational studies suggest that conservative feeding regimens, including slowly advancing enteral feed volumes, reduce the risk of NEC. However, slow feed advancement may delay establishment of full enteral feeding and may be associated with metabolic and infectious morbidities secondary to prolonged exposure to parenteral nutrition. To determine effects of slow rates of enteral feed advancement on the incidence of NEC, mortality, and other morbidities in very preterm or VLBW infants. We used the standard Cochrane Neonatal search strategy to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 5), MEDLINE via PubMed (1966 to June 2017), Embase (1980 to June 2017), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to June 2017). We searched clinical trials databases, conference proceedings, previous reviews, and reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-randomised trials. Randomised or quasi-randomised controlled trials that assessed effects of slow (up to 24 mL/kg/d) versus faster rates of advancement of enteral feed volumes upon the incidence of NEC in very preterm or VLBW infants. Two review authors assessed trial eligibility and risk of bias and independently extracted data. We analysed treatment effects in individual trials and reported risk ratio (RR) and risk difference (RD) for dichotomous data, and mean difference (MD) for continuous data, with respective 95% confidence intervals (CIs). We used a fixed-effect model for meta-analyses and explored potential causes of heterogeneity via sensitivity analyses. We assessed the quality of evidence at the outcome level using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. We identified 10 RCTs in which a total of 3753 infants participated (2804 infants participated in one large trial). Most participants were stable very preterm infants of birth weight appropriate for gestation. About one-third of all participants were extremely preterm or extremely low birth weight (ELBW), and about one-fifth were small for gestational age (SGA), growth-restricted, or compromised in utero, as indicated by absent or reversed end-diastolic flow velocity (AREDFV) in the fetal umbilical artery. Trials typically defined slow advancement as daily increments of 15 to 20 mL/kg, and faster advancement as daily increments of 30 to 40 mL/kg. Trials generally were of good methodological quality, although none was blinded.Meta-analyses did not show effects on risk of NEC (typical RR 1.07, 95% CI 0.83 to 1.39; RD 0.0, 95% CI -0.01 to 0.02) or all-cause mortality (typical RR 1.15, 95% CI 0.93 to 1.42; typical RD 0.01, 95% CI -0.01 to 0.03). Subgroup analyses of extremely preterm or ELBW infants, or of SGA or growth-restricted or growth-compromised infants, showed no evidence of an effect on risk of NEC or death. Slow feed advancement delayed establishment of full enteral nutrition by between about one and five days. Meta-analysis showed borderline increased risk of invasive infection (typical RR 1.15, 95% CI 1.00 to 1.32; typical RD 0.03, 95% CI 0.00 to 0.05). The GRADE quality of evidence for primary outcomes was "moderate", downgraded from "high" because of lack of blinding in the included trials. Available trial data do not provide evidence that advancing enteral feed volumes at daily increments of 15 to 20 mL/kg (compared with 30 to 40 mL/kg) reduces the risk of NEC or death in very preterm or VLBW infants, extremely preterm or ELBW infants, SGA or growth-restricted infants, or infants with antenatal AREDFV. Advancing the volume of enteral feeds at a slow rate results in several days of delay in establishing full enteral feeds and may increase the risk of invasive infection.