What it is: A low-lying placenta that covers part or all of the inner opening of the cervix.
Health dangers: The baby's exit from the uterus can be blocked during delivery. And as the cervix begins to thin and dilate in preparation for labor, blood vessels that connect the placenta to the uterus may tear, resulting in bleeding. If the bleeding is severe and occurs during labor and delivery, it can endanger the lives of mother and baby.
Risk factors: Smoking; illegal drug use; being older than 35; previous uterine surgery, such as a c-section or D&C (dilation and curettage, which involves scraping the uterine lining); carrying multiples; previous births.
Signs and symptoms: In some cases, there are no symptoms, and placenta previa is discovered during a routine ultrasound. If this occurs in the first half of pregnancy, it will most likely correct itself. During the second half of pregnancy, the condition is marked by painless vaginal bleeding.
Diagnosis and treatment: A hospital exam and an ultrasound. If the bleeding stops, as it often does, your physician will continue to monitor you and your baby. You will probably be treated with a corticosteroid to help your baby's lungs mature if you are likely to deliver before 34 weeks. At 36 weeks, if you haven't yet delivered, your provider may suggest testing the amniotic fluid (obtained by amniocentesis) to see if your baby's lungs are mature. If they are, she will likely recommend a c-section at that time to prevent risks associated with any future bleeding episodes.
If the bleeding doesn't stop, or you go into labor, your doctor will probably recommend a prompt c-section. Cesarean delivery is recommended for nearly all women with placenta previa because the birth canal is blocked by the placenta, and c-sections can usually prevent severe bleeding.