All the literature states that a mother should not pump her breasts until the baby is 1 month of age. This is almost criminal advice in my opinion! Prolactin is the hormone responsible for making the breast milk. Oxytocin is the hormone responsible for letting the milk let down and come out of the nipple. When the placenta comes out of the mother’s body this is the catalyst that gets the milk making components in line for making milk for the baby. Prolactin is highest in a woman’s blood right after she has her baby. This level falls a little after the first week of life only to surge up when the infant nurses or the nipples are stimulated. This level of prolactin continues to decrease over the first month and again surges highest when the nipples are stimulated as when the baby is nursing or the mother is pumping.
The prolactin surges in the beginning and during the first few weeks of life are very important! A newborn baby or a premature baby may not be the best at breastfeeding or stimulating the nipples during the first week or two of life. Many times babies are sleepy and if they are not gaining weight or their bilirubin levels are rising then it becomes a vicious cycle. My best tag line is that if your baby is sleepy or not feeding well something needs to be stimulating your nipples so that you can take advantage of this early time period to set the bar high for a healthy milk supply. When both breasts are stimulated at the same time this too causes a prolactin surge!
reference: K. Wambach, B. Spencer,, Breastfeeding and Human Lactation, Sixth Edition, 2021, Jones and Bartlett Learning, LLC