My niece is seven months into a healthy pregnancy but she has what seems to be a regular period every month since she has been pregnant what could it?

Bleeding: Its unusual. Sometimes the placenta is over the cervix, that's placenta previa. Early obn it can be implantation bleeding but would not suspect that here. Follow closely with ultrasound, it's unusual but wit good rest, and possibly oral or vaginal progesterone, the bleeding, though maybe not the outcome, could get improvement. Good luck.