It is not normal to have a period while pregnant. if a woman is pregnant and bleeding, it could possibly be a miscarriage (the body is getting rid of the fetus for some reason) and a miscarriage is harmful to the baby (it will die.)
Furthermore, women do not menstruate (have a period) while pregnant.
Each month, the uterus grows a thick blood-rich lining in preparation for an egg to embed there (a nice home for a fetus for about 9 months.) If it is not fertilized, the lining and the egg will flush out (the period.) If it is fertilized, the pregnancy will continue with the fetus growing in the uterus.
So, a period cannot happen while a woman is pregnant, unless it is detrimental/deadly to the fetus (the fetus and the home.)