Letdown is simply the release of milk from the breast. It's a reflex that happens when nerves in your breasts are stimulated (usually by your baby's sucking) and signal the release of oxytocin, a hormone that prompts tiny muscles around your milk-producing cells to contract, squeezing milk into the ducts. How long it takes can vary from woman to woman or even from feeding to feeding, but it's usually anywhere from a few seconds to a few minutes.
The letdown reflex ensures that your baby gets enough milk. It's a pretty powerful thing, and can be triggered not just by your baby's sucking, but also by sexual contact and even psychological factors. For example, once you've been breastfeeding for a while, you may find that the sound of your baby's cries (or any baby crying) can get your milk flowing.
Most moms describe letdown as a tingly, pins-and-needles sensation in their chest, which can happen right after birth or even several weeks into breastfeeding. The tickly feeling is actually milk making its way through the ducts to your nipples. Letdown usually occurs in both breasts at the same time, so it's perfectly normal to drip from one breast while your baby feeds from the other (you can use nursing pads to catch the leakage).
Copyright 2009 Meredith Corporation.