1) Pang 
• (n. pl.) The pains which succeed childbirth, as in expelling the afterbirth.
(af´tәr-pānz) pains following expulsion of the placenta, due to contraction of the uterus, seen particularly in multiparas due to vigorous periodic contractions of the puerperal uterus. It is noticeable particularly when the infant nurses, and may be severe; the intensity usually decreases to become mil...
Cramping triggered by the contractions
Aft'er·pains` noun plural (Medicine) The pains which succeed childbirth, as in expelling the afterbirth. 
Type: Term Pronunciation: af′ter-pānz Definitions: 1. Painful cramplike contractions of the uterus occurring after childbirth.
Cramping sensations that are triggered by the contracting of the uterus in the postpartum phase as it shrinks down to its pre-pregnant size. Afterpains are more common and painful in subsequent pregnancies. With each pregnancy the tone of the uterus becomes more relaxed, which makes the uterus contract more forcefully as it shrinks to its pre-preg....
[n] - pains felt by a woman after her baby is born
normal contractions of the uterus after childbirth that usually occur for the first few days after delivery 
noun pains felt by a woman after her baby is born; associated with contractions of the uterus
Cramping triggered by the contractions of the uterus in the postpartum phase as it shrinks and makes its normal descent back into the pelvis.