The breastfeeding let-down reflex, also called the milk-ejection reflex MER , is an automatic natural reaction that happens in your body as your baby breastfeeds. Prolactin is responsible for making more breast milk , and oxytocin triggers the let-down or release of your breast milk. Here you will learn about the signs of a letdown, how it feels, the tips for stimulating the flow of breast milk, and how to deal with a slow or painful letdown. You may also notice the signs of milk letdown when you are not breastfeeding or pumping. It can come on quickly and unexpectedly at feeding time, when you hear your child cry, during a warm shower, or during sexual activity.