A Cochrane review [Abstract] 1 included 34 studies, 17 of which (961 mothers) provided data used in the analyses. Interventions used included different pumps versus hand expression or another type of pump, different protocols with or without adjunct behaviour like relaxation or massage. Mothers provided with a relaxation tape produced more milk than mothers who were not (mean difference (MD) 34.70 ml/single expression, 95% CI 9.51 to 59.89). Any method plus warming the breast versus not warming the breast showed increased milk expression (MD 11.94ml, 95% CI 7.94 to 15.94; 1 trial, n=468). A lower milk volume over 6 days was reported when comparing hand expression to the electric pump; other studies of the same pump using different measures did not find a significant difference. No evidence of difference in volume was found with simultaneous or sequential pumping, or between manual and electric pumps studied. Hand expression and lower cost pumps may be as effective, or more effective, than large electric pumps for some outcomes. Maternal satisfaction, adverse effects on mothers and economic effects of interventions were poorly reported.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals), by inconsistency (heterogeneity in interventions and outcomes), and by potential reporting bias (trial sponsored by pump manufacturer).
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