Is it bad if I bleed when I am pregnant?

I never consider bleeding during pregnancy normal. Common? Yes. Main point is to find out why you are bleeding. 30% of people bleed in the first trimester of pregnancy. Sometimes it's the start of a miscarriage, a lot of times not. Sometimes it is from a polyp, or sex or placenta previa. Later in pregnancy it can be from a placental abruption or labor with cervical change. Heavy bleeding always worries me more than spotting.

Bleeding during pregnancy is something that needs to be reported to the healthcare provider, therefore it is not normal. Usually when one thinks of bleeding during pregnancy the complications of placenta preia and placenta abruption come to mind. However there are sometimes that the bleeding is not associated with a complication. For example, a number of women experience some bleeding in the early portion of the first trimester. This is referred to as implantation bleeding and is associated with the fertilized egg burrowing into the lush lining of the uterus. In the second and third trimester of pregnancy there might be bleeding following intercourse or vaginal examinations. During pregnancy there is increased blood flow to the cervix and the tissue is more friable. Therefore pressure and/or manipulation of the cervix may result in bleeding. And finally, in the third trimester the woman may experience bleeding as the mucous plug is expelled as the cervix begins to efface and dilate in preparation for labor.

Bleeding pregnancy always requires an evaluation. You should call your health care provider.
At the same time, one in five pregnancies experience bleeding during the first trimester, and half of these go on to be healthy pregnancies. Early, light bleeding may come from the engorged blood vessels that lie very close to the surface of the cervix. This is more likely to occur after a procedure such as cervical cultures, a pap smear, or after sex. Sometimes the pregnancy implanting into the uterine lining causes bleeding. Sometimes it is a pregnancy that has stopped developing and a miscarraige is inevitable.
Bleeding after the first trimester is more likely to be a concern. If the placenta implants over or near the cervical opening, a placenta previa, there may be painless bleeding. If the placenta begins to separate from the uterine wall, placenta abruptio, there may be bleeding, but there is more likely to be unrelenting pain. Again, the bleeding can be from a harmless source such as the cervix.