A nurse is planning care for a client with placenta previa. Which of the following laboratory and diagnostic measures should be included? Select all that apply

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 occurs when the placenta develops in the lower uterine segment, directly over or near the internal cervical os. This anatomical positioning places the fragile vascular network of the placenta in the direct path of any instrument or finger entering the cervical canal. Unlike a normally implanted placenta in the fundus, a previa is highly susceptible to mechanical trauma, where even minor contact can shear the maternal-fetal interface. Because the lower segment is thin and lacks the robust contractile power of the upper myometrium, the resulting decidual bleeding cannot be easily tamponaded, leading to rapid exsanguination.

Rationale for correct answer

3. The most appropriate explanation is that a vaginal examination may precipitate life-threatening hemorrhage by causing direct mechanical trauma to the placenta. Because the placenta is located over the cervix, digital manipulation can tear the placental sinuses, leading to an immediate and profuse flow of maternal blood. This hemorrhage can result in hypovolemic shock for the mother and catastrophic hypoxia for the fetus within minutes. Avoiding vaginal entry is the most critical safety precaution in the management of suspected or confirmed placenta previa.

Rationale for incorrect answers

1. While cervical stimulation can sometimes release prostaglandins that might theoretically irritate the uterus, inducing preterm labor is not the primary reason for avoiding the exam. The immediate and far more dangerous risk is vascular disruption and hemorrhage. In the context of placenta previa, the focus shifts from the timing of labor to the circulatory integrity of the mother. Contractions would actually be secondary to the massive bleeding that an exam would likely trigger.

2. Maternal hypotension is a symptom of hypovolemic shock, which is the result of the hemorrhage, not the direct effect of the examination itself. A vaginal exam does not have a vasovagal effect that primarily causes hypotension in these clients. The drop in blood pressure would be a secondary consequence of the massive blood loss initiated by the trauma to the placenta. Therefore, while hypotension is a major concern, the explanation provided to the client must focus on the cause (hemorrhage) rather than the symptom.

4. Altered fetal heart rate patterns, such as bradycardia or late decelerations, are signs of fetal distress that occur after placental perfusion is compromised. A vaginal exam does not directly change the fetal heart rhythm through nerve stimulation; rather, it causes bleeding that reduces the oxygen supply to the fetus. The pathophysiological sequence begins with hemorrhage, leading to placental insufficiency, which then manifests on the monitor. Explaining the risk of bleeding is more direct and accurate for the client's understanding.

Test-taking strategy

• Identify the Diagnosis: The client has suspected placenta previa, which is a high-alert condition for bleeding.
• Assess the Risk: Evaluate each option for its level of urgency and severity. While labor (1) and heart rate changes (4) are important, "life-threatening hemorrhage" (3) represents the highest priority and greatest risk to life.
• Apply the "Nothing per Vagina" Rule: In nursing education, the absolute contraindication for third-trimester bleeding is a vaginal exam. The reason is always the risk of puncturing or detaching the placenta.
• Differentiate Cause vs. Effect: Recognize that hypotension (2) and heart rate changes (4) are outcomes of bleeding. Choice 3 identifies the primary event that the nurse is trying to prevent.

Take home points

• Digital vaginal examinations are strictly contraindicated in clients with placenta previa due to the risk of placental tearing.
• The primary clinical goal in placenta previa is to prevent any trauma that could lead to maternal exsanguination.
• Ultrasound is the only safe diagnostic method used to determine the exact location of the placenta.
• Any client with third-trimester bleeding must be treated as having placenta previa until imaging proves otherwise.