Breastfeeding represents the best feed for infant, nevertheless this task is particularly challenging for mothers. Sleep time and quality are undeniably reduced in the postpartum period. No study has demonstrated the relationship between slow wave sleep and lactation. Here, we self-report a unique experimental case during which the mother registered her own sleep with SUUNTO 9 watch and quantified her milk volume, blind to sleep parameters. This case report highlighted an interesting strong correlation between stage N3 (slow wave sleep) duration and milk production. It also demonstrated that this production is linked positively to subjective sleepiness in the morning and breast tension, and negatively to the number of awakenings. These results emphasized the need of sleep preservation, especially N3 sleep during breastfeeding. Splitting nighttime infant care among parents, saving mother’s sleep as much as possible during the first part of the night, could help improving lactation.