Afterpains are contractions in the uterus that occur during breastfeeding. This is due to a surge of oxytocin, which causes the uterus to contract. These may range from period-like cramps to strong labor-like contractions and can be more severe with second and subsequent babies.
Lactation. (2016, August 6). In Wikipedia, The Free Encyclopedia. Retrieved 18:58, August 6, 2016, from https://en.wikipedia.org/w/index.php?title=Lactation&oldid=733287323