Placenta previa occurs when the placenta is lying low in your uterus and is either right next to or covering the cervix.  In a normal pregnancy the placenta would be near the top of the uterus, well away from the cervix.  During your early ultrasounds your doctor will look to see where the placenta is in your uterus.  Placenta previa isn't usually a problem early in pregnancy but can become a problem later in pregnancy causing bleeding and possibly premature birth.

During your mid-pregnancy ultrasound, usually done around 19 or 20 weeks, the doctor will determine where your placenta is lying.  If your placenta is low in the uterus, right next to or covering the cervix, your doctor will need to monitor your pregnancy more closely.  It is possible for the placenta to migrate into a more normal, higher, position later in the pregnancy so being diagnosed with placenta previa during your second trimester doesn't necessarily mean you will still have placenta previa later in your pregnancy.  The placenta itself does not move, but as your uterus continues to expand it may end up further away from your cervix.  Only about 10% of women who are found to have placenta previa during their mid-pregnancy ultrasound still have it when they deliver their baby.

You will be scheduled for a follow up ultrasound so that your doctor can keep an eye on the location of your placenta, depending on if the placenta previa resolves itself or not you may have multiple ultrasounds throughout the remainder of your pregnancy.  If placenta previa persists your doctor will likely prescribe pelvic rest and you'll be advised to take it easy, being especially careful to avoid any activities that may provoke vaginal bleeding.  Your doctor will monitor you for bleeding throughout the remainder of your pregnancy. If you do have bleeding or contractions you will be hospitalized so you can be monitored closely. With placenta previa you will not be able to deliver vaginally, which is why your doctor will want to keep an eye out for any signs of preterm labor.  

Placenta previa can happen to any one, however, there are a few factors that increase your risk of placenta previa, they are:

  • You are pregnant with multiples (twins or higher)
  • You have previously had a c-section
  • You have previously had uterine surgery (such as D&C or fibroid removal)
  • You smoke
  • You use cocaine
  • You age and the number of kids you have had can also increase your risk

If you are diagnosed with placenta previa talk to your doctor about what that means for you, what you need to do to ensure a safe delivery, etc.  As stated above, placenta previa found earlier in pregnancy often resolves later in pregnancy, however, it may persist so your doctor will monitor you closely throughout your pregnancy so they can ensure they are on top of any complications that may arise.