Placenta praevia

The placenta is the organ responsible for providing oxygen and nutrients to the baby during pregnancy. The placenta is usually attached to one of the inner walls of the uterus. 

Placenta previa is the complete or partial insertion of the placenta into the lower segment of the uterus, which can obstruct the internal cervical os, which is the exit route for the baby.

Depending on the relationship of the placenta to the os, it is classified into the following types

• Complete: The cervix is completely covered by the placenta.
• Partial: The cervix is partially covered by the placenta.
• Marginal: The placenta reaches the edge of the cervical os but does not extend beyond it.
• Minor: The edge of the placenta is less than 2 cm from the cervix.

The exact cause is unknown, but there are several contributing factors:

• Multiple pregnancies: The placenta takes up more volume and is more likely to obstruct the cervix.
• Anterior uterine scar: The incidence increases with the number of previous cesarean deliveries.
• Multiparity: parity and over 35 years of age.
• Smoking: doubles the risk.

This location can make it easier for bleeding to occur during pregnancy. This bleeding is usually mild, but sometimes it can be severe and life-threatening to the baby.
Placenta previa can be life-threatening to both the baby and the mother. Placenta previa is the most common cause of bleeding in the third trimester.

The definitive diagnosis is made by transvaginal ultrasound. A differential diagnosis must be made with vasa previa, placental abruption, and uterine rupture.
Treatment depends on the type of placenta previa. If the placenta is completely occluded: elective cesarean section at 38 weeks. If the placenta is marginal or minor and there is no bleeding, it is best to allow labor to proceed spontaneously.