Having placenta previa means your placenta is located near the bottom of the uterus -- instead of on the side or closer to the top -- so it covers all or part of the inner opening of the cervix. This means the baby's exit from the uterus can be blocked during delivery.
In some cases, placenta previa has no symptoms and is usually discovered during a routine ultrasound. In the second half of pregnancy, the condition may cause temporary, painless vaginal bleeding. Placenta previa can happen to anyone, but occurs most often in women who are pregnant with multiples or for the second or third time, who smoke or use drugs, who are older than 35, or who have had uterine surgery like a c-section or D&C (dilation and curettage, which involves scraping the uterine lining).
Placenta previa is usually not a problem early in pregnancy, since it often corrects itself. But if it doesn't go away, it can cause bleeding or other complications, which may mean you'll have to deliver your baby early. In about 10 percent of cases, women who were diagnosed with placenta previa at some point during pregnancy will still have it as labor and delivery approaches. If this is the case, you'll need to have a c-section.
If you're bleeding and the doctor discovers you have placenta previa, don't panic. The bleeding usually stops and your doctor will continue to monitor you and the baby. If it's earlier than 34 weeks, you'll probably be treated with corticosteroids to help your baby's lungs mature just in case he has to be delivered early. After 36 weeks, your doctor may decide to do a c-section to prevent risks associated with any future bleeding episodes.