The Merit Study (Manual Expression pRemature InfanTs)

Manual Expression of Breast Milk One of the major contributing factors for the cessation of breast feeding in the premature population of infants is decreased milk production. Because most premature infants are unable to initially feed at the breast, artificial methods to maintain milk supply such as manual and electric pump expression have been explored.

Studies by Flaherman et al. and Slusher et al. both used a randomized design to address manual versus pump expression and its effect on milk volume. Flaherman et al. studied a population of 68 full-term infants feeding poorly at the breast for two months after delivery in a United States academic medical center and randomized the mother to either manual expression or electric pump expression. Slusher et al. allocated mothers of 65 premature infants admitted to an African special care nursery to manual expression, manual powered pedal pump or an electric pump for six-ten days after delivery. Both studies found the electric pump to yield higher volumes of milk than manual expression. Slusher et al. found a statistically significant increase in milk volume with the electric pump when compared to manual expression (p<0.01). No mean differences in demographics between the three groups were found. Flaherman et al. also reported higher milk volumes with the electric pump but the comparison failed to reach statistical significance (p=0.07). Although failing to reach statistical significance on milk volume, Flaherman, followed participants for two months and reported higher rates of continued breastfeeding among the mothers who had initially used hand expression (p=0.02). In addition, Flaherman measured self -efficacy using the Breastfeeding Self-Efficacy Scale-Short Form (BSES-SF) at baseline, one week, one moth and two months after delivery. However, there were no significant differences between the groups for breastfeeding self-efficacy.

Two studies investigated a combination of manual and electric pump expression. Morton combined hand expression and electric pumping whereas Ohyama used manual expression or electric pump expression. In the study by Morton) a prospective observational design was used to examine milk production for eight weeks after delivery for mothers who were instructed to use an electric pump and manually express as much as possible in the first three days post-partum with no particular sequencing. In this sample of 67 mothers of premature infants, Morton was able to find an increased milk production at two weeks for those mothers that hand expressed greater than five times a day (p<0.05). Ohyama also studied mothers of premature infants in a Japanese neonatal intensive care unit using a crossover design that studied a combination of manual and electric pump expression techniques. The mothers were sequentially allocated to either manual or electric pump expression and then alternated the method until seven sessions had been completed for each method. Net milk yield was significantly higher with manual expression (p<0.05) as compared to pump expression in the first 48 hours after delivery. Both of these studies support the potential benefit of manual expression for early removal of colostrum prior to the onset of mature milk.

A pilot feasibility study using a combined sequence of manual and pump expression intervention for the first three days after delivery was conducted on the mothers of premature infants whose infants were hospitalized in a NICU in the proposed study population and setting. Mothers of premature infants (n=6) were asked by staff nurses in the intra-partum and post-partum units to perform manual expression prior to electric pump expression for the first three days after delivery and record milk volumes on a breastfeeding log for three weeks after delivery. Women who had not begun an initial expression within six hours after delivery were initially excluded, based on previous literature that states the longer the delay in time from delivery to expression can serve as an important variable in overall milk production. Due to the infeasibility of the women being able to begin their first pumping session within six hours of delivery due to complications of delivery or other logistical issues within the healthcare setting, the inclusion criteria for recruitment was extended from six hours to 24 hours after delivery. The intervention of manual expression was able to be delivered on all of the mothers in the study thus providing important information on the feasibility of teaching this intervention in this population of mothers. However, because only half of the mothers in the study were able to complete the log, revisions in the amount and duration of study variables for the larger study have been considered.

Limitations of Previous Studies on Manual Expression Of the studies reviewed, only three addressed premature infants and only two were randomized trials thus causation is difficult to establish. There was conflicting evidence whether electric pump expression or manual expression yielded higher milk volumes and a standard sequencing method was not always employed in the research design. All of the studies reported relatively low sample sizes and failed to mention the use of a power analysis which can lead to a Type I error. Most of the studies were focused on physiological outcomes as the primary measure and did not incorporate a theoretical framework. The studies were based on the physiological theory that early and frequent pump expression after delivery is essential to maintain milk supply in mothers who may be separated from their infants or when infants are feeding poorly.

Despite the mixed results of previous studies it is becoming standard practice for many hospitals to instruct all mothers on manual expression as a result of the recommendation of the Baby-Friendly Hospital Initiative (BFHI). The BFHI is a global initiative endorsed by WHO and the United Nations Children's Fund (UNICEF) whose primary goal is to assist all mothers in being able to successfully initiate and sustain breastfeeding. The BFHI recognizes hospitals that are successful in meeting their guidelines for breastfeeding quality and outcomes. The number of U.S. hospitals applying for the BFHI certification has increased since 2010 when the U.S. Department of Health and Human Services incorporated the practices promoted into federal goals. As part of the BFHI global criteria, 80% of mothers need to report that they have been taught how to hand express their milk for both mothers feeding at the breast and for those mothers who are separated from their babies. The duration of manual expression was not defined by the BFHI and previous studies incorporating manual expression have not measured how many days of manual expression may be optimal. Of the studies reviewed that incorporated manual expression as an independent variable, most were not in combination with electric pump expression. The duration of manual expression varied across all studies; anywhere from three to eight days after delivery.

As previously discussed, lactogenesis II is marked by the onset of copious milk secretion after birth and the delivery of the placenta and occurs anywhere from two to eight days postpartum. Due to the variability of when mature milk is created, the timing of the colostrum period may vary per individual. Comparing the duration of manual expression may reveal insights into the optimal timing of this expression technique for mothers of premature infants. No studies reviewed focused on the duration of manual expression as an independent variable. This study will be the first to focus on the duration of manual expression as the primary variable of interest.