Placenta previa is the attachment of the placenta to the wall of the uterus in a location that completely or partially covers the uterine outlet (opening of the cervix).
- Bleeding after the 20th week of gestation is the main symptom of placenta previa.
- An ultrasound examination is used to establish the diagnosis of placenta previa.
- Treatment of placenta previa involves bed rest and limitation of activity. Tocolytic medications, intravenous fluids, and blood transfusions may be required depending upon the severity of the condition.
- A Cesarean delivery is required for complete placenta previa.
- Other complications of pregnancy can be associated with placenta previa, but the majority of women deliver healthy babies.
What is placenta previa?
Placenta previa is the most common cause of painless bleeding in the later stages of pregnancy (after the 20th week). The placenta is a temporary organ that joins the mother and fetus and transfers oxygen and nutrients from the mother to the fetus. The placenta is disk-shaped and at full term measures about seven inches in diameter. The placenta attaches to the wall of the uterus (womb). Placenta previa is a complication that results from the placenta implanting either near to, or overlying, the outlet of the uterus (the opening of the uterus, the cervix).
Because the placenta is rich in blood vessels, if it is implanted near the outlet of the uterus, bleeding can occur when the cervix dilates or stretches.
What are the types of placenta previa?
The types of placenta previa include:
- Complete placenta previa occurs when the placenta completely covers the opening from the womb to the cervix.
- Partial placenta previa occurs when the placenta partially covers the cervical opening
- Marginal placenta previa occurs when the placenta is located adjacent to, but not covering, the cervical opening.
The term low-lying placenta or low placenta has been used to refer both to placenta previa and marginal placenta previa. Sometimes, the terms anterior placenta previa and posterior placenta previa are used to further define the exact position of the placenta within the uterus as defined by ultrasound examinations.