Technically speaking, you cannot have a true period and be pregnant at the same time, since a period indicates release of materials that lead to pregnancy.  However, there is the possibility that you are having bleeding in early pregnancy that can be mistaken for a period.  Some of the causes of bleeding in early pregnancy can be:

–  Implantation bleeding.  This occurs when the embryo burrows into the wall of the uterus and occurs around 5 days after ovulation.  The timing is such that it could appear to be an early menstrual period.

–  Birth control pills.  If you get pregnant while you are on the pill, you may have intermittent bleeding before you it is obvious that you’re pregnant.

–  Ectopic pregnancy.  An ectopic pregnancy is one in which the fetus is not inside the uterus.  This can cause bleeding.

–  Threatened, completed or uncompleted miscarriage.  Bleeding during early pregnancy can indicate that a miscarriage has occurred or may occur.

If bleeding during early pregnancy is confused for a period, it can lead to confusion regarding your due date.  If this is the case, an ultrasound may provide a more accurate due date.

Can you have your period if you are pregnant?