Lay summary
The first 1,000 days are the foundation for lifelong health and wellbeing. Although exclusive breastfeeding is recommended until around 6 months of age, relatively few mothers in New Zealand reach this milestone. Perceived insufficient milk supply is reported to be a leading cause of early cessation of breastfeeding, yet it is currently unknown whether the perception of insufficient milk supply is associated with actual low breast milk supply. This study will recruit 150 mother-pēpi dyads and determine actual breast milk intakes of 3 month old infants (using gold standard stable isotope methods). This will allow us to determine whether breast milk volumes produced are associated with the perception of breast milk supply. The results will be beneficial to health professionals working with lactating mothers with milk supply concerns.