Donor Milk Expression Habits: Can we Favor Hindmilk Banking for Extremely Preterm Infants?

Background: Extremely preterm infants often receive donor milk. Hindmilk, which is released more than 3 minutes after letdown, could be advantageous due to its elevated levels of fat and calorie density. Donor milk expression habits may influence milk composition but have not yet been investigated. This study aims to assess the practices of milk donors and the feasibility of hindmilk expression. Methods: Active milk donors in Québec were questioned using an online survey about their milk expression habits and whether hindmilk donation would be acceptable to them. Answers were analyzed using mixed methods. Results: Of 181 donors, 126 fully completed the questionnaire (70%); 57% reported expressing donated milk between breastfeeds; 15% reported simultaneously breastfeeding while expressing donated milk from the other breast; 12% reported breastfeeding their baby on each breast, then expressing donated milk (hindmilk). The majority (66%) would be willing to change their habits most or all the time to provide hindmilk for preterm infants. The main themes invoked by respondents in open-ended answers were altruism and gratitude for being able to help others. However, 15% commented on the complexity of milk expression or that adding further complexity might discourage them from donating. Conclusions: Expression practices are variable, which may lead to variability in donor milk composition. Most donors would agree to change their expression habits in favor of giving hindmilk to help the most fragile infants. More information is needed on how changing recommendations for milk expression might impact the supply and composition of donor milk.