What is Placenta Previa?
The placenta partially or completely covers the cervical opening, blocking the normal route for delivery and causing vaginal bleeding, especially in the third trimester. It occurs in roughly 1 in 200 pregnancies and is a leading cause of antepartum hemorrhage (StatPearls).
Pathophysiology
The placenta implants on the lower uterus. As the cervix dilates, the lower uterine segment separates from the upper segment. The placenta cannot stretch to follow the cervix, and it bleeds.
Risk Factors
- Advanced maternal age. Risk rises in women over 35.
- Multiple gestations. A uterus that has carried more than one fetus is at higher risk.
- Increased parity. More prior births, higher risk.
- Past cesarean births. Prior cesarean predisposes to previa in the next pregnancy.
- Past uterine curettage. Scarring affects implantation.
Types
Classified by how much of the os the placenta covers:
- Low-lying placenta. Implants in the lower uterus rather than the upper.
- Marginal implantation. The placenta's edge nears the cervical os.
- Partial placenta previa. Part of the os is covered.
- Total placenta previa. The placenta occludes the entire os.
Signs and Symptoms
- Bright red bleeding. When the placenta cannot stretch to follow the cervix, bleeding starts suddenly and can frighten the patient.
- Painless. Bleeding in placenta previa is classically painless and may stop as abruptly as it began.
Diagnostic Tests
- Ultrasound. The first and most common test, and it detects previa early. Transvaginal ultrasound is the gold standard for diagnosis and is safe in previa; it is more accurate than the transabdominal view (RCOG; StatPearls).
Medical Management
- IV therapy. Replaces blood lost during bleeding.
- No vaginal examinations. They can trigger fatal hemorrhage.
- External monitoring. Use external equipment for uterine contractions and fetal heart sounds, not internal.
Surgical Management
- Cesarean delivery. If the placenta obstructs more than 30% of the cervical os, vaginal delivery is not feasible and cesarean is recommended.
Nursing Management
Nursing Assessment
- Assess baseline vital signs, especially blood pressure. The physician may order blood pressure every 5 to 15 minutes.
- Assess fetal heart sounds.
- Monitor uterine contractions to track labor progress.
- Weigh perineal pads used during bleeding to estimate blood loss.
- Position her side-lying when bleeding occurs.
Nursing Diagnosis
- Fear related to the outcome of pregnancy due to bleeding.
Nursing Interventions
- Assess fetal heart sounds and share them so she knows her baby's status.
- Let her vent to ease emotional stress.
- Assess any bleeding or spotting and act on it.
- Answer her questions honestly to build trust.
- Include her in planning the care plan for her and the baby.
Evaluation
- She discusses her concerns with the team.
- She states that hearing the fetal heartbeat reassures her of the baby's safety.
Protecting two patients at once is the work here. With a steady team and a supported mother, these pregnancies can be brought through safely.
Frequently Asked Questions
What is placenta previa?
It is when the placenta implants low in the uterus and partially or completely covers the cervical opening. That position blocks the path for vaginal delivery and tends to bleed, classically painless bright red bleeding in the third trimester.
How common is placenta previa?
It occurs in about 1 in 200 pregnancies (StatPearls). The risk rises with prior cesarean births, advanced maternal age, multiple gestations, high parity, and previous uterine surgery.
Why are vaginal exams never done with placenta previa?
A digital or speculum exam can disturb the placenta covering the cervix and trigger sudden, heavy, potentially fatal hemorrhage. Diagnosis and monitoring rely on ultrasound and external fetal and contraction monitoring instead.
How is placenta previa diagnosed?
By ultrasound. Transvaginal ultrasound is the gold standard and is safe in previa, giving a clearer view of the placental edge and cervix than the transabdominal approach (RCOG; StatPearls).
Can a baby be delivered vaginally with placenta previa?
No, not when the placenta covers the os. Cesarean delivery is required because the placenta blocks the birth canal and vaginal delivery would cause catastrophic bleeding.
What is the main danger of placenta previa?
Hemorrhage for the mother and the consequences of blood loss and prematurity for the baby. Placenta previa also raises the risk of placenta accreta spectrum, especially after a prior cesarean, which can mean major bleeding at delivery (ACOG).