Prenatal Testing During the Third Trimester
Key Points
- Third-trimester testing assesses ongoing fetal well-being and guides timing of delivery.
- Common tools include ultrasound growth/placenta assessment, NST, BPP, AFI, and movement counts.
- Nonreassuring results often trigger stepwise escalation to additional testing or delivery planning.
- Nursing care emphasizes preparation, interpretation support, and urgent escalation readiness.
Pathophysiology
In late pregnancy, placental reserve and uteroplacental perfusion determine fetal oxygenation and growth. Antepartum testing evaluates whether fetal compensation remains adequate or deterioration is developing.
Reduced movement, nonreactive heart-rate patterns, oligohydramnios, and abnormal biophysical findings can indicate hypoxic risk, placental insufficiency, or other high-acuity conditions requiring rapid intervention.
Classification
- Ultrasound surveillance domain: Growth trends, placental location, amniotic-fluid assessment, and presentation.
- Heart-rate surveillance domain: NST and vibroacoustic stimulation response.
- Composite surveillance domain: BPP and AFI scoring.
- Escalation domain: CST or delivery-planning pathways for persistent nonreassurance.
Nursing Assessment
NCLEX Focus
Compare fetal status trends over time; single reassuring snapshots do not replace pattern surveillance.
- Assess indication for testing and maternal symptom context.
- Verify fetal movement pattern and daily count understanding.
- Monitor tracing quality and response criteria during NST/CST workflows.
- Identify maternal factors affecting interpretation (medications, sleep cycle, glucose status).
- Escalate promptly for persistent nonreassuring findings.
Nursing Interventions
- Educate on why each surveillance test is ordered and what results mean.
- Prepare patient positioning/comfort and reduce anxiety during testing.
- Implement protocol-driven escalation after nonreactive or abnormal results.
- Reinforce home instructions for fetal movement count and triage triggers.
- Coordinate follow-up schedule and multidisciplinary planning if risk increases.
Reassurance Delay
Waiting too long after repeated nonreassuring fetal surveillance can increase risk of preventable hypoxic injury.
Pharmacology
| Drug Class | Examples | Key Nursing Considerations |
|---|---|---|
| antenatal-corticosteroids | Imminent preterm-delivery contexts | Supports fetal lung maturation when early delivery risk is high. |
| antihypertensives-in-pregnancy | Hypertensive-complication contexts | Maternal stabilization often improves fetal surveillance reliability and safety. |
Clinical Judgment Application
Clinical Scenario
A 34-week patient with hypertension has a nonreactive NST, reduced movement report, and low AFI.
Recognize Cues: Multiple nonreassuring fetal-status indicators. Analyze Cues: Pattern suggests uteroplacental compromise risk. Prioritize Hypotheses: Priority is urgent maternal-fetal reassessment and escalation. Generate Solutions: Perform protocol escalation (BPP/CST as indicated) and notify obstetric team. Take Action: Initiate continuous monitoring and delivery-readiness planning. Evaluate Outcomes: Timely intervention prevents progression to severe fetal compromise.
Related Concepts
- care-in-the-third-trimester-of-pregnancy - Routine third-trimester visits identify candidates for enhanced testing.
- conditions-limited-to-pregnancy - Hypertensive/placental disorders are common triggers for surveillance.
- fetal-growth-and-development - Growth and placental dynamics underlie test interpretation.
- choosing-a-birthing-place - Surveillance outcomes may change recommended delivery setting.
- person-and-family-centered-care - Communication around nonreassuring tests requires clear shared planning.
Self-Check
- What differentiates a reactive from nonreactive NST?
- How should care escalate after combined abnormal NST and low AFI?
- Which teaching points improve reliability of home fetal movement counts?