Afterpains are sharp pains in the belly that occur in the first few days after childbirth. Although they may hurt, afterpains help reduce uterine bleeding. They also help shrink the uterus back to the size it was before you were pregnant. You are most likely to notice these pains when you breastfeed. Breastfeeding triggers the release of oxytocin, which causes the uterus to contract. The pains usually start to go away by the third day after childbirth.