Breast milk expression with a breast pump increases the risk of contaminating milk with pathogenic bacteria; how to decontaminate breast pumps is controversial. The aim of this study was to investigate maternal adherence to updated French guidance on the breast milk collection process, including breast pump decontamination, and to identify potential sources of increased bacterial counts in breast milk in order to improve prevention messages to mothers.

Descriptive prospective study conducted between November 2015 and April 2016 in a French tertiary perinatal center. Oral and written instructions on the breast milk collection process and breast pump decontamination were given to mothers by trained healthcare professionals. Mothers whose neonates were admitted to the neonatal care unit and expressing milk for the human milk bank were eligible if breast milk bacterial counts before pasteurization were≥10⁶ colony-forming units (cfu)/mL for total aerobic flora or ≥10⁴ cfu/mL for Staphylococcus aureus. Maternal adherence to the guidance was investigated with a questionnaire and a face-to-face interview.

One hundred and fourteen mothers with neonates admitted to the neonatal care unit expressed milk for the milk bank; 44 (39%) were eligible and 29 (66%) included: most of them (76%) with increased counts of total aerobic flora in breast milk and 24% with increased counts of S. aureus. At least three divergences from the guidance provided were reported for 16 mothers (55%). The most frequent ones were inadequate storage of the breast pump collection kit (62%), ineffective decontamination of the breast pump collection kit (52%), inappropriate cleaning of the breast pump (48%), and inadequate breast milk transport from home to hospital (31%).

Despite standardized instructions, mothers with increased bacterial counts in breast milk frequently declared several divergences from the guidance on the breast milk collection process. Giving mothers and any person of their choice repeated clear instructions with illustrated guidance, demonstrations, and practice may help improve the microbiological safety of expressed breast milk.