Placenta previa happens when the placenta implants low and covers the cervix. If you have placenta previa you'll need to have a cesearean delivery.
There are three types of previa (depicted in the photo above).
Normally, the placenta will implant far away from the cervix. Most often it implants on the back wall of the uterus (normal placenta in the photo) or at the top of the uterus (called the "fundus"). Less often, it implants on the front wall ("anterior placenta") - this is not a worry for delivery, but it may mean that it is harder to feel your baby move.
Placentas that implant near or over the cervix are problematic. If it partially or totally covers the cervix (see photo above) a cesearean section will be the only delivery option.
The cervix is the the outlet through which the baby exits the womb. If the placenta covers the cervix completely, a cesearean section is the only mode of delivery possible.
A partial placenta previa may or may not require an operative delivery. It depends on how close the edge of the placenta is to the cervix.
If the placenta implants low on the uterine wall, near or at the edge of the cerivix, there is a chance it will "resolve". Many women think the placenta "moves out of the way" but this is a misconception. As the uterus grows and expands, the relative location of the placenta to the cervix can be greater - giving the illusion of having moved.
Placenta previa is seen on ultrasound examination. You may be told to look for signs of bleeding and activities to avoid.
Sometimes, symptoms occur before the diagnosis and this is the first you become aware of the issue. The classic sign of placenta previa is painless vaginal bleeding. It can cause severe bleeding during pregnancy and delivery.
Vaginal delivery is not possible with a complete previa.
If you have placenta previa, you might bleed throughout your pregnancy and during your delivery. Your health care provider will recommend avoiding activities that might cause contractions, including having sex, douching, using tampons, or engaging in activities that can increase your risk of bleeding, such as running, squatting, and jumping.
Any vaginal bleeding should be reportd to your healthcare provider right away.