Background: Successful transition from parenteral nutrition to full enteral feedings during the immediate neonatal period is associated with improved growth in preterm infants. Lactase is the last of the major intestinal disaccharidases to develop in preterm infants. Because of inadequate lactase activity, preterm infants are unable to digest lactose. Lactase preparations could potentially be used to hydrolyze lactose in formulas and breast milk to minimize lactose malabsorption in preterm infants.
Objectives: To assess the effectiveness and safety of the addition of lactase to milk compared to placebo or no intervention for the promotion of growth and feeding tolerance in preterm infants.
Primary outcomes: Weight gain expressed as g/kg/day, growth expressed as weight, length and head circumference percentile for gestational age, assessed at birth and at 40 weeks post-menstrual age, days to achieve full enteral feeds.
Secondary outcomes: Several common outcomes associated with preterm birth, and adverse effects.
Search strategy: Electronic and manual searches were conducted in January 2005 of Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2004), MEDLINE (1966-Jan 2005), EMBASE (1980-Jan 2005) and CINAHL (1982-Jan 2005), personal files, bibliographies of identified trials and abstracts by the Pediatric Academic Societies' and the European Society of Pediatric Research Meetings published in Pediatric Research.
Selection criteria: Types of studies: Randomized or quasi-randomized controlled trials.
Participants: Preterm infants < 37 weeks gestational age.
Intervention: Addition of lactase to milk versus placebo or no intervention.
Data collection and analysis: The standard methods of the Cochrane Neonatal Review Group were followed independently by the reviewers to assess study quality and report outcomes. Treatment effects, calculated using RevMan 4.2, included relative risk (RR), risk difference (RD) and mean difference (MD), all with 95% confidence intervals (CI). A fixed effect model was used for meta-analyses. Heterogeneity tests were not performed as only one study was identified.
Main results: One study enrolling 130 infants of 26 - 34 weeks postconceptual age (mean postnatal age at entry 11 days) was identified and no identified study was excluded. The study was a double blind randomized controlled trial of high quality. Lactase treated feeds were initiated when enteral feedings provided > 75% of daily intake. None of the primary outcomes outlined in the protocol for this review and only one of the secondary outcomes, necrotizing enterocolitis (NEC), were reported on. The RR for NEC was 0.32 (95% CI 0.32 (0.01, 7.79); the RD was -0.02 (95% CI -0.06, 0.03) (a reduction which was not statistically significant). There was a statistically significant increase in weight gain at study day 10 in the lactase treated feeds group but not at any other time points. Overall, there ws not a statistically significant effect on weight gain. No adverse effects were noted.
Authors' conclusions: The only randomized trial to date provides no evidence of significant benefit to preterm infants from adding lactase to their feeds. Further research regarding effectiveness and safety are required before practice recommendations can be made. Randomized controlled trials comparing lactase vs placebo treated feeds and enrolling infants when enteral feeds are introduced are recommended. The primary and secondary outcomes for effectiveness and safety should include those identified in this review.