Breakthrough bleeding, or abnormal vaginal bleeding between periods, can be a sign of pregnancy, but there are also other factors that can cause this symptom to occur, according to WebMD. Breakthrough bleeding can occur early in pregnancy when the fertilized egg implants itself on the uterine lining, explains Mayo Clinic.
Often called spotting, breakthrough bleeding during pregnancy can also be caused by increased blood flow to the pelvis, explains Mayo Clinic. Heavier bleeding prior to 12 weeks may be caused by miscarriage or ectopic pregnancy, according to WebMD, and a doctor should be consulted. Bleeding after 12 weeks may indicate placenta previa or another serious issue.
Breakthrough bleeding does not always point to pregnancy, as WebMD explains that this is also a symptom of polycystic ovary syndrome, pelvic organ infections or pelvic inflammatory disease. Spotting may also occur in women who are taking certain kinds of birth control pills or using an intrauterine device to prevent pregnancy.