1. Stages of Pregnancy Slideshow Pictures
2. Early Pregnancy Symptoms
3. Conception (Egg to Embryo) Slideshow Pictures

Medical Author:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• What is placenta previa?
• What are the types of placenta previa?
• Who is at risk for placenta previa?
• What causes placenta previa?
• What are the symptoms of placenta previa?
• How is placenta previa diagnosed?
• What is the treatment for placenta previa?
• What are possible complications of placenta previa?
• Can placenta previa be prevented?
• What is the prognosis (outlook) for placenta previa?
• Placenta Previa At A Glance
• Find a local Obstetrician-Gynecologist in your town
• Pregnancy: Placenta Previa Index

The placenta may be located in the lower part of the uterus either covering or adjacent to the cervical outlet for a number of reasons. The placenta normally migrates away from the cervical opening as the pregnancy progresses, so women in the earlier stages of pregnancy are more likely to have placenta previa than are women at term. Although up to 6% of women between 10 and 20 weeks' gestation will have some evidence of placenta previa on ultrasound examination, 90% of these cases resolve on their own as the pregnancy progresses.

Placenta previa that persists beyond the 20th week of gestation can be due to abnormalities of the uterus that promote attachment of the placenta in the lower regions of the uterus or to factors that require an increased size of the placenta.

Uterine factors that can predispose to placenta previa include scarring of the upper lining tissues of the uterus. This can occur because of prior Cesarean deliveries, prior instrumentation (such as D&C procedures or curettages for miscarriages or induced abortions) of the uterine cavity, or any type of surgery involving the uterus.

When the placenta must grow larger to compensate for decreased function (lowered ability to deliver oxygen and/or nutrients), there is an increased chance of developing placenta previa since the surface area of the placenta will be larger. Examples of situations in which there is need for greater placenta function and a resultant increase in risk for placenta previa include multiple gestation, cigarette smoking in the mother, and living at high altitude.