Cramping and red blood can often indicate a complication. If the blood is brown, that means it's old and is just ejecting itself as the body is known to do in order to stay healthy (coincidentally, it's possible to have more than one period after pregnancy begins, as implantation of the fertilized egg and/or hormone fluctuations can induce the sloughing of cells from the Uterine wall. Be safe before sorry, always.