BACKGROUND: This is an update of a 2008 Cochrane review. Breastfeeding is important. However, not all infants can feed at the breast and methods of expressing milk need evaluation.
OBJECTIVES: To assess acceptability, effectiveness, safety, effect on milk composition, contamination and cost implications of methods of milk expression.
SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2014), CINAHL (1982 to March 2014), conference proceedings, secondary references and contacted researchers.
SELECTION CRITERIA: Randomised and quasi-randomised trials comparing methods at any time after birth.
DATA COLLECTION AND ANALYSIS: Three authors independently assessed trials, extracted data and assessed risk of bias.
MAIN RESULTS: This updated review includes 34 studies involving 1998 participants, with 17 trials involving 961 participants providing data for analysis. Eight studies compared one or more types of pump versus hand expression and 14 studies compared one type of pump versus another type of pump, with three of these studies comparing both hand expression and multiple pump types. Fifteen studies compared a specific protocol or adjunct behaviour including sequential versus simultaneous pumping protocols (five studies), pumping > 4 times per day versus < 3 times per day (one study), provision of a milk expression education and support intervention to mothers of preterm infants versus no provision (one study), provision of audio/visual relaxation to mothers of preterm infants versus no specific relaxation (two studies), commencing pumping within one hour of delivery versus between one to six hours (one study), breast massage before or during pumping versus no massage (two studies, of which one also tested a second behaviour), therapeutic touch versus none (one study), warming breasts before pumping versus not warming breasts (one study), combining hand expression with pumping versus pumping alone (one study) and a breast cleansing protocol versus no protocol (one study). There were insufficient comparable data on outcomes to undertake meta-analysis and data reported relates to evidence from single studies. Only one of the 17 studies examining maternal satisfaction/acceptability provided data in a way that could be analysed, reporting that mothers assigned to the pumping group had more agreement with the statement 'I don't want anyone to see me pumping' than mothers in the hand expression group and the statement 'I don't want anyone to see me hand expressing' (n = 68, mean difference (MD) -0.70, 95% confidence interval (CI) -1.25 to -0.15, P = 0.01), and that mothers found instructions for hand expression were clearer than for pumping (n = 68, MD 0.40, 95% CI 0.05 to 0.75, P = 0.02). No evidence of a difference was found between methods related to adverse effects of milk contamination (one study, n = 28, risk ratio (RR) 0.89, 95% CI 0.62 to 1.27, P = 0.51), (one study, n = 142 milk samples, MD 0.20, 95% CI -0.18 to 0.58, P = 0.30), (one study, n = 123 milk samples, MD 0.10, 95% CI -0.29 to 0.49, P = 0.61), (one study, n = 141 milk samples, MD -0.10, 95% CI -0.46 to 0.26, P = 0.59 ); or level of maternal breast or nipple pain or damage (one study, n = 68, MD 0.02, 95% CI -0.67 to 0.71, P = 0.96). For the secondary outcomes, greater volume was obtained when mothers with infants in a neonatal unit were provided with a relaxation tape or music-listening interventions to use while pumping, when the breasts was warmed before pumping or massaged while pumping. Initiation of milk pumping within 60 minutes of birth of a very low birthweight infant obtained higher mean milk quantity in the first week than the group who initiated pumping later. No evidence of difference in volume was found with simultaneous or sequential pumping or between pumps studied. Differences between methods was found for sodium, potassium, protein and fat constituents; no evidence of difference was found for energy content. No consistent effect was found related to prolactin change or effect on oxytocin release with pump type or method. Economic aspects were not reported. Most studies were classified as unclear or low risk of bias. Most studies did not provide any information regarding blinding of outcome assessment. Fifteen of the 25 studies that evaluated pumps or products had support from the manufacturers.
AUTHORS' CONCLUSIONS: The most suitable method for milk expression may depend on the time since birth, purpose of expression and the individual mother and infant. Low-cost interventions including early initiation when not feeding at the breast, listening to relaxation music, massage and warming of the breasts, hand expression and lower cost pumps may be as effective, or more effective, than large electric pumps for some outcomes. Small sample sizes, large standard deviations, and the diversity of the interventions argue caution in applying these results beyond the specific method tested in the specific settings.