There are three types of placenta previa, but all result in approximately the same signs and symptoms. These types are:

• Total placenta previa (placenta previa centralis). The internal cervical os (the small opening of the cervix that dilates during the first stage of labor) is completely covered by the placenta.
  
  
• Partial placenta previa (placenta previa partialis). The internal cervical os is partly covered by the placenta.
  
  
• Marginal placenta previa (placenta previa marginalis). The placenta is near, but not covering, the internal cervical os. This may not cause as much bleeding as the other types.

There is another condition related to placenta previa called low-lying placenta. This term is used to describe several circumstances:

• Placenta previa experienced in the second trimester.
  
  
• Placenta that lies low in the uterus but whose proximity to the internal cervical os has not been determined.
  
  
• The edge of the placenta lies within 2 to 3 centimeters (0.8 to 1.2 inches) of the internal cervical os.