Effect of nipple shield use on milk removal: a mechanistic study

Viviane Silva Coentro; Sharon Lisa Perrella; Ching Tat Lai; Alethea Rea; Kevin Murray; Donna Tracy Geddes

doi:10.1186/s12884-020-03191-5

Effect of nipple shield use on milk removal: a mechanistic study

BMC Pregnancy Childbirth. 2020 Sep 7;20(1):516. doi: 10.1186/s12884-020-03191-5.

Authors

Viviane Silva Coentro¹, Sharon Lisa Perrella², Ching Tat Lai¹, Alethea Rea³, Kevin Murray⁴, Donna Tracy Geddes¹

Affiliations

¹ School of Molecular Sciences, Faculty of Science, The University of Western Australia, M310, 35 Stirling Highway, Western Australia, 6009, Crawley, Australia.
² School of Molecular Sciences, Faculty of Science, The University of Western Australia, M310, 35 Stirling Highway, Western Australia, 6009, Crawley, Australia. sharon.perrella@uwa.edu.au.
³ Mathematics and Statistics, School of Engineering and Information Technology, Murdoch University, 90 South Street, Western Australia, 6150, Murdoch, Australia.
⁴ School of Population and Global Health, Faculty of Health and Medical Sciences, Population and Global Health, The University of Western Australia, M431, 35 Stirling Highway, Western Australia, 6009, Crawley, Australia.

Abstract

Background: Concerns 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.

Methods: A 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.

Results: Of 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).

Conclusions: This experimental data suggests that nipple shield use may reduce milk removal. Close clinical monitoring of breastfeeding mothers using nipple shields is warranted.

Keywords: Milk removal; Nipple pain; Nipple shield; Pumping.

MeSH terms

Adult
Breast Milk Expression / instrumentation*
Female
Humans
Infant
Infant, Newborn
Mechanical Phenomena
Milk Ejection*
Nipples*
Pain / prevention & control*
Protective Devices*
Random Allocation