A nurse is assessing a client at 34 weeks gestation with painless, bright red vaginal bleeding. Which of the following diagnostic evaluations should the nurse anticipate first?

Placenta previa is a condition where the placenta implants in the lower uterine segment, partially or completely covering the cervical os. It presents with painless bright red bleeding in the third trimester. Risk factors include multiparity, advanced maternal age, and prior cesarean section. Diagnosis is confirmed by ultrasound, and management involves maternal stabilization, avoidance of digital cervical examination, and fetal surveillance. Severe bleeding can cause maternal hypovolemia and fetal compromise, necessitating prompt evaluation and delivery if unstable.

Rationale for correct answer/s

3. Biophysical profile is indicated to assess fetal well-being when maternal bleeding occurs. It evaluates fetal movement, tone, breathing, and amniotic fluid volume. In placenta previa, maternal stability must be ensured, but fetal compromise requires immediate assessment. The fetus and oxygenation are prioritized, making this the correct initial evaluation.

Rationale for incorrect answers

1. Transvaginal ultrasound is the gold standard for diagnosing placenta previa, but it is not the first step when acute bleeding occurs. Immediate fetal assessment is prioritized. Although placental location is important, maternal-fetal stabilization precedes definitive imaging.

2. Immediate digital cervical examination is contraindicated in suspected placenta previa because it can provoke catastrophic hemorrhage. The cervix should not be manipulated until placental location is confirmed. This makes it unsafe and inappropriate as an initial evaluation.

4. MRI is useful for diagnosing placenta accreta spectrum disorders, especially in surgical planning. However, it is not appropriate in acute bleeding scenarios. The imaging modality is too advanced for initial stabilization and does not address immediate fetal compromise.

Test-taking strategy

• Identify the hallmark presentation: painless, bright red bleeding in late pregnancy strongly suggests placenta previa.
• Apply safety principles: avoid interventions that increase risk of hemorrhage, such as digital cervical examination.
• Use prioritization frameworks: maternal stabilization and fetal well-being are immediate priorities.
  • ABCs: airway, breathing, circulation must be stabilized in the mother.
  • Fetal assessment: biophysical profile provides rapid information about fetal oxygenation and movement.
• Rule out distractors:
  • Ultrasound is diagnostic but not the first step in acute bleeding.
  • MRI is advanced imaging, not urgent stabilization.
  • Cervical examination is unsafe in placenta previa.
• Select the option that addresses fetal compromise while maintaining maternal safety.

Take home points

• Placenta previa presents with painless, bright red bleeding in the third trimester.
• Digital cervical examination is contraindicated due to risk of hemorrhage.
• Biophysical profile is essential for immediate fetal assessment in maternal bleeding.
• Ultrasound confirms diagnosis, but stabilization and fetal evaluation come first.

Placenta previa is characterized by the implantation of the placenta in the lower uterine segment, which is definitively diagnosed through sonographic visualization. Transvaginal ultrasound is the gold standard for diagnosis, as it allows for precise measurement of the distance between the placental edge and the internal cervical os. During the assessment, the sonographer also evaluates the retroplacental interface and the uterine wall to rule out morbidly adherent placenta, while clinical assessment confirms the absence of myometrial irritability. Successful management depends on identifying the exact degree of coverage to determine the safety of expectant management versus the necessity of a surgical delivery.

Rationale for correct answers

1. The primary diagnostic finding in placenta previa is the visualization of the placenta covering or near the internal cervical os. Transvaginal ultrasound provides high-resolution images that allow the clinician to classify the previa as complete, partial, or marginal based on the percentage of coverage. If the placental edge is within 2 cm of the os, it is clinically managed as a previa due to the high risk of hemorrhage. This finding confirms the anatomical malposition that defines the condition.

2. A soft, non-tender uterine wall is a hallmark clinical finding that distinguishes placenta previa from abruptio placentae. In previa, the bleeding originates from the placental site without significant myometrial irritation or intrauterine pressure elevation. On ultrasound, the uterine wall appears thin and relaxed, consistent with the clinical lack of abdominal rigidity. This finding is crucial for differential diagnosis, as it indicates that the bleeding is not caused by a premature separation of a normally implanted placenta.

4. Visualizing an intact umbilical cord insertion is a standard part of the ultrasound evaluation to rule out vasa previa or velamentous insertion. In placenta previa, the cord typically inserts into the placental mass normally, although the mass itself is malpositioned. Ensuring that the vessels are not crossing the os unprotected (vasa previa) is vital because fetal exsanguination occurs much more rapidly if the vessels themselves are ruptured. This assessment confirms the stability of the fetal circulatory attachment.

5. Ultrasound may reveal possible signs of placenta accreta spectrum, which is a frequent and dangerous co-morbidity of placenta previa. Sonographic markers include the loss of the retroplacental clear zone, abnormal placental lacunae, and hypervascularity at the bladder-uterine interface. This is especially relevant if the client has a history of previous cesarean sections, as the placenta can grow into the old surgical scar. Early identification of invasion allows for complex surgical planning and prevents catastrophic postpartum hemorrhage.

Rationale for incorrect answers

3. Clear evidence of uterine rupture is a catastrophic finding that is not a characteristic feature of placenta previa. Uterine rupture involves a full-thickness tear of the myometrium, usually manifesting on ultrasound as fetal parts outside the uterus, a retracted uterus, or massive hemoperitoneum. This condition presents with sudden, sharp pain and maternal shock, contrasting with the painless bleeding seen in previa. While both are emergencies, their pathophysiological mechanisms and sonographic appearances are entirely different.

Test-taking strategy

• Identify Diagnostic Findings: The question asks what the nurse should see on an ultrasound report for a client with known or suspected placenta previa.
• Focus on Anatomy: Select Choice 1 because it defines the location of the problem. Select Choice 4 and 5 because they represent the standard anatomical survey performed during a placental ultrasound.
• Use Differential Diagnosis: Recall that previa is painless (2) while abruption is painful. A soft uterus on assessment correlates with a normal-looking myometrium on ultrasound, making Choice 2 correct.
• Rule out Catastrophes: Eliminate Choice 3 because uterine rupture is a separate, distinct obstetric emergency that is not a standard finding or a common result of placenta previa itself.
• Select All That Apply: Ensure that the selected options (1, 2, 4, 5) provide a comprehensive picture of the diagnostic and safety assessments required for this condition.

Take home points

• Transvaginal ultrasound is the most accurate method for determining the distance between the placenta and the cervical os.
• A soft, non-tender uterus helps differentiate placenta previa from the board-like rigidity of abruptio placentae.
• Placenta previa in a client with prior uterine surgery necessitates a high suspicion for placenta accreta spectrum.
• Sonographic evaluation must also confirm normal umbilical cord insertion to exclude vasa previa.