Placenta Previa

Placenta previa occurs when the placenta is attached closer to the bottom of the uterus than it should be. In this position, the placenta either partially or completely blocks the opening in the cervix. Depending on the extent of the placenta previa, it can put the mother and baby at risk if a vaginal delivery is attempted.

 

Placenta Previa Defined

Normally, the placenta is attached to the inside wall of the uterus, either up along the side or the top of it. Placenta previa occurs when the placenta is attached closer to the bottom and either partially or completely blocks the opening in the cervix. This happens in about 1 out of every 200 pregnancies. The most common symptom of placenta previa is painless bleeding in the later stages of pregnancy.
 
When placenta previa is diagnosed earlier in the pregnancy (which is possible using ultrasound), it is monitored very closely. In cases of partial placenta previa, where the placenta partially covers the cervix early in the pregnancy, it's possible for the placenta to move away from the cervix as the pregnancy progresses. If a partial placenta previa still exists when true labor begins, a vaginal delivery may be possible. However, in cases of complete placenta previa, where the placenta covers the entire cervix, a cesarean delivery is usually recommended.
 

Placenta Previa and Cesarean Delivery

Why does placenta previa become serious if a normal vaginal delivery is attempted? With placenta previa, as the cervix dilates, it usually causes the placenta to separate from the wall of the uterus too early.
 This can result in serious bleeding that can be fatal for both the mother and/or the baby. Because of this, cesarean delivery is usually recommended in such cases.
 
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD