Placenta previa, which occurs in one in 200 births, can be a serious complication of pregnancy. Placenta previa means that the placenta, the organ that supplies nutrients to the growing fetus, implants low on the uterine wall, partially or completely covering the cervix, the opening from the uterus to the vagina. Because the placenta has many blood vessels, heavy bleeding can occur if the cervix begins to dilate. Cesarean section is usually necessary, and serious fetal and maternal complications may occur.
Hemorrhage
If the cervix starts to dilate, painless bright red bleeding occurs. In undiagnosed cases of placenta previa, hemorrhage may occur quickly and can be exacerbated if a medical practitioner attempts to do a cervical examination and detaches the placenta further or puts his finger through part of it. One third to one half of all women with placenta previa need blood transfusions to replace blood loss.
Fetal Complications
Preterm delivery is common in placenta previa, occurring in two thirds of cases, Healthline states. Fetal hemorrhage can complicate preterm delivery in placenta previa; babies may require blood transfusions. Prematurity is the cause of 60 percent of infant deaths related to placenta previa, NYU Langone Medical Center reports. Placenta previa also increases the risk of poor growth in utero because the placenta may not implant well, leading to an increased risk of birth defects and neonatal death or stillbirth if hemorrhage does occur.
Placental Abruption
Placenta previa can also cause premature separation of the placenta from the uterine wall, called placental abruption. Severe blood loss may occur quickly in cases of abruption, and both mother and fetus can die from hemorrhage. Immediate cesarean delivery is required in cases of placental abruption.
Placenta Accreta
Placenta accreta occurs when the placenta grows too deeply into the uterine wall and doesn't separate spontaneously after delivery. Placenta accreta is more common in people with placenta previa; one to five percent of women with placenta previa also have placenta accreta. Placenta accreta is even more common in those who have had previous cesarean sections. As many as one third to one half of women with previous cesarean delivery and placenta previa will develop placenta accreta, Healthline states.
