Abstract
BackgroundConcerns about reduced milk transfer with nipple shield (NS) use are based on evidence from studies with methodological flaws. Milk removal during breastfeeding can be impacted by infant and maternal factors other than NS use. The aim of this study was to control electric breast pump vacuum strength, pattern and duration across multiple study sessions to determine if NS use reduces milk removal from the breast.MethodsA within-subject study with two groups of breastfeeding mothers (infants < 6 months) were recruited; Control Group (CG): no breastfeeding difficulties; Pain Group (PG) used NS for persistent nipple pain. Mothers completed three randomised 15 min pumping sessions using the Symphony vacuum curve (Medela AG); no NS, fitted NS, and a small NS. Sessions were considered valid where the applied vacuum was within 20 mmHg of the set vacuum. Milk removal was considered as pumped milk volume, and also percentage of available milk removed (PAMR), which is calculated as the pumped volume divided by the estimated milk volume stored in the breast immediately prior to pumping.ResultsOf 62 sessions (all: n = 31 paired sessions) a total of 11 paired sessions from both PG (n = 03) and CG (n = 08) were valid (subset) with and without a fitted NS. Only 2 small shield sessions were valid and so all small shield measurements were excluded. Both pumped volumes and PAMR were significantly lower with NS use for all data but not for subset data. (All: Volume and PAMR median: no NS: 76.5 mL, 69%, Fitted NS: 32.1 mL, 41% respectively (volume p = 0.002, PAMR p = 0.002); Subset: Volume and PAMR median: no NS: 83.8 mL, 72%; Fitted NS: 35.2 mL, 40% (volume p = 0.111 and PAMR p = 0.045). The difference in PAMR, but not volume, was statistically significant when analysed by linear mixed modelling. A decrease of 10 mmHg was associated with a 4.4% increase in PAMR (p = 0.017).ConclusionsThis experimental data suggests that nipple shield use may reduce milk removal. Close clinical monitoring of breastfeeding mothers using nipple shields is warranted.
Highlights
Concerns about reduced milk transfer with nipple shield (NS) use are based on evidence from studies with methodological flaws
Data were collected for up to three pumping sessions from 31 mothers in total (PG n = 09, Control Group (CG) n = 22), and results reported for 31 paired sessions of pumping without and with a fitted nipple shield
Valid data were obtained for 11 paired sessions to provide subset data for 11 mothers (PG n = 03, CG n = 08)
Summary
Concerns about reduced milk transfer with nipple shield (NS) use are based on evidence from studies with methodological flaws. Concerns about reduced milk transfer are based on studies performed more than three decades ago where both breastfeeding and breast pump use with a nipple shield resulted in lower milk transfer volumes than when breastfeeding or pumping without a nipple shield [12, 16]. Methodological issues such as small sample size, sampling prior to the establishment of a full milk supply, and absence of confirmation of adequate milk supply all call into question the validity of the reported results [10]. In the pumping study, it was assumed that the breast was completely drained at the end of the pumping session, the duration of pumping prior to milk ejection was not accounted for, and achievement and maintenance of a set cycling pressure and pattern were not confirmed [16]
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