Bleeding in the first trimester of pregnancy is relatively common and doesn't necessarily indicate a problem with the pregnancy. A 2003 study of 221 pregnant women published in the September issue of the "Human Reproduction" journal found that 9 percent of the women who became pregnant during the study bled during the first eight weeks of pregnancy, often around the time of their period. The source of this bleeding was not identified, but other researchers suggest the causes of this bleeding vary.
Implantation bleeding is not specifically proven in the medical community, but it's thought to be bleeding that follows the implantation of the fertilized egg into the wall of the uterus. It typically occurs within the first 10 days to two weeks of pregnancy, states MayoClinic.com. This type of bleeding is considered normal and relatively common. The bleeding typically is lighter than a normal menstrual period and lasts a day, though it might mimic your menses and last for two days. It is not heavier than your normal period, MayoClinic.com states.
When a fertilized egg implants itself outside of the uterus -- in the lining of the fallopian tubes, for example -- the pregnancy is ectopic and not viable. The fertilized egg cannot survive in the area in which it has implanted and the risk to the mother's health is significant. In addition, ectopic pregnancies can rupture the fallopian tubes, causing fertility issues. If your bleeding is accompanied by abdominal pain or severe, stabbing pain, contact your doctor immediately for medical help.
About 10 percent to 20 percent of pregnancies end in miscarriage, MayoClinic.com reports. If your body isn't ready, the fertilized egg has problems, you have issues with blood clotting, or your immune system is triggered by the fertilized egg, a miscarriage can occur. One important thing for women to note: MayoClinic.com says that stress is not a factor in miscarriage. The reasons aren't always clear.
When to Call the Doctor
Contact your obstetrician if your bleeding lasts more than a day, is heavy or is accompanied by pain in the shoulder or abdomen. If you are bleeding and experience sudden, stabbing pain, you need immediate medical attention. In addition, if you suspect you are pregnant, are bleeding lightly and feel a constant, unproductive need to use the toilet, you need medical help, as you might have an ectopic pregnancy.