Babies do not take the same amount of milk in at every breastfeeding, and test weighing gives the staff a good idea of how much milk the baby takes in over a period of time. Your baby still may not be able to consistently demonstrate feeding cues or breastfeed effectively at discharge, but after observing feedings for 8 to 24 hours, the NICU staff will be able to work with you to develop a better discharge breastfeeding plan. It continues to be beneficial once you are home. Many mothers report that it seems to help babies get to the breast more effectively sooner, and it helps them maintain milk production. Plus, it just feels good to cuddle this way.
Most babies do learn to handle let-down as they mature.
Until then, you might try pumping through the let-down immediately before a feeding. Another option is to take the baby off the breast until the milk flow slows. The milk then travels uphill during a let-down, which slows the flow. When your baby has the basic idea of nutritive sucking but cannot seem to do it consistently, try pumping one breast while nursing your baby on the other. You may want to halt a breastfeeding if you or your baby gets too frustrated or when feedings are taking more than 40 to 45 minutes.