Implantation of the fertilized embryo in the uterus causes light bleeding during pregnancy, according to WebMD. Known as implantation bleeding, it is normal during early pregnancy. A miscarriage or an ectopic pregnancy can cause heavy bleeding accompanied by cramping and pain.
Implantation bleeding is not always noticeable and occurs in roughly 25 percent of pregnant women, who sometimes mistake it for a light period, reports WebMD. It usually occurs six to 12 days after conception. The blood is lighter in color and flow than menstrual blood, and mild abdominal cramping may accompany it. Implantation bleeding, when it occurs, takes place before morning sickness or other more noticeable symptoms of pregnancy.
When vaginal bleeding occurs late in pregnancy, it may signal that the body is preparing to deliver the baby, according to WebMD. Days or weeks before labor begins, expulsion of the mucus plug covering the uterus occurs; it is not uncommon for small amounts of blood to be present in it. Contractions, discharge, lower backache and abdominal pressure indicate early labor as well.
When dealing with bleeding during pregnancy, a doctor may ask the expectant mother to wear a pad to monitor the amount and color of blood, states WebMD. Women should not use tampons while bleeding during pregnancy.