haha I'm not sure if you're asking this seriously or not....but ok.
Women's periods stop once they get pregnant. Once an egg has been fertilized, there is not need for the body to flush out unfertilized eggs. Which is what a woman's period is. Once a month a women ovulates (passes an egg) if the egg does not get fertilized, then a women gets her period about two weeks later. To flush out the lining of the uterus and get rid of the unfertilized egg. So, once a women gets pregnant, they no longer ovulate...which means they no longer bleed. A couple months after your gilfriend has the baby she will continue getting her periods. She will also bleed for about 6 weeks after giving birth. Very heavily for about a week, and then it will slow to menstral like bleeding.
Anyways, it's too bad that your so ignorant about all of this. I guess I take my husband for granted! lol