When your baby stimulates your nipple by sucking she triggers the automatic reflex that makes milk available in your breasts, the let-down reflex. The stimulation sends a message to the pituitary gland to release oxytocin. This hormone not only makes you feel love and calm, but also prompts milk-producing cells in your mammary glands to empty their milk into the milk ducts leading to your nipple by contracting the muscles around the glands.
The let-down reflex can also be triggered when you hear your baby cry in hunger or even simply by you thinking about your baby. If your milk flow is stimulated before you start a feed the milk will leak from your nipple and may come out with some speed as a spray. If you’re not ready to feed you can try and stop the milk flow by pressing firmly on the sides of your breast.
When you first start to feed you might also feel stomach cramps as the oxytocin released also prompts the uterus to contract back to its pre-pregnancy side, however you may also feel nothing at all. The more children you have had, the more likely you will be to feel the uterus contract.