Giving birth to a baby, doesn't always mean that you will have enough milk supply to meet the needs of your little one. We often work with moms who are struggling to make more milk. Women who have risk factors for low milk supply yet are told to "let the baby bring the milk in" and not pump are being set up for failure. I often hear from mothers who have been told by their pediatrician or post-partum nurse to leave establishing milk supply up to the newborn. While a full term, vigorous baby may be up to the task, a sleepy newborn, perhaps one dealing with jaundice or weight issues, will not do an effective job removing milk and stimulating the breast.
The fear of creating an oversupply is also valid, yet this is often an issue when mothers start a pumping schedule too early in addition to nursing so that they can build their freezer stash. I, and many other lactation consultants no doubt, have heard from mothers who perhaps have PCOS (ploy-cystic ovarian syndrome), hypothyroidism or a previous nursing experience with insufficient supply who are discouraged to use the pump from the very beginning.
What about the case of a mother whose 3rd child, born at 37 weeks and just 6 lb had to be in the NICU for respiratory issues? That mom had previously had significantly lower supply from the right breast and her 2 older babies preferred the left. This time, she used the pump early on and was able to establish nearly equal supply on both sides. She tended to have clogged ducts on the right side and she had to massage the area often to encourage effective milk removal. So, we wondered which came first for her, the low supply which led her older babies to prefer the other side or the clogged ducts which a newborn couldn't work with, resulting in low supply on that side... This time with a hospital grade pump, milk removal was better on that side and eventually as baby got more vigorous, he was able to nurse effectively and maintain supply on both sides. I am leaning towards the latter.
With cases such as this, I am motivated to recommend pumping when there are any blips on the radar for a breastfeeding dyad. I also encourage medical practitioners involved to take a good history of both mom and baby to help them maximize supply with early yet temporary use of a pump.