A 35-year-old multigravida at 39 weeks of gestation with an unfavorable cervix (Bishop score 6) is admitted for induction of labor due to gestational diabetes. Before starting cervical ripening with misoprostol, the attending obstetrician wishes to confirm fetal well-being and rule out any contraindications to induction. Which investigation is most appropriate to assess fetal status and uterine contractility before initiating induction?

Explanation

## Pre-Induction Fetal Assessment **Key Point:** Cardiotocography (CTG) or non-stress test (NST) is the standard investigation to assess fetal well-being immediately before induction of labor. It evaluates fetal heart rate reactivity and detects any signs of fetal distress or uterine contractions that may contraindicate induction. ### Role of CTG/NST Before Induction 1. **Fetal heart rate reactivity** — confirms fetal well-being and neurological integrity 2. **Baseline variability** — assesses fetal autonomic function 3. **Detects fetal distress** — identifies decelerations or abnormal patterns that may contraindicate induction 4. **Establishes baseline** — provides a reference for comparison during labor induction 5. **Detects spontaneous contractions** — may indicate labor has already begun ### CTG Interpretation (Before Induction) **Reassuring (Normal):** - Baseline FHR: 110–160 bpm - Variability: 5–25 bpm - Accelerations: ≥2 accelerations in 20 minutes - No decelerations **Non-reassuring findings that may delay/contraindicate induction:** - Baseline <110 or >160 bpm - Reduced variability (<5 bpm) - Recurrent late decelerations - Variable decelerations with slow recovery **High-Yield:** A reactive NST (with accelerations and normal variability) is reassuring and allows safe progression to induction. A non-reactive NST warrants further investigation (BPP or ultrasound) before proceeding. **Clinical Pearl:** In a multigravida with gestational diabetes, NST is especially important because maternal hyperglycemia increases fetal hypoxia risk; a reassuring NST confirms the fetus can tolerate the stress of labor induction. ### Why CTG/NST Is Preferred Over Alternatives **Advantages:** - **Rapid & bedside** — performed in minutes, no delay to induction - **Real-time assessment** — detects acute fetal distress immediately - **Guides induction safety** — abnormal CTG may prompt delay or alternative management - **Standard of care** — universally recommended before induction ### Why Other Investigations Are Not Routine Pre-Induction Tests - **Doppler ultrasound (umbilical artery):** Assesses placental insufficiency and fetal growth restriction; not a routine pre-induction test unless specific concern (e.g., IUGR, hypertension) - **Contraction stress test (CST):** Outdated; largely replaced by NST + BPP; rarely used before induction in modern practice - **Fetal biophysical profile (BPP):** Comprehensive but time-consuming; reserved for abnormal NST or specific indications (oligohydramnios, IUGR), not routine pre-induction screening ### Decision Algorithm ```mermaid flowchart TD A[Unfavorable cervix, ready for induction]:::outcome --> B[Perform NST/CTG]:::action B --> C{NST reactive?}:::decision C -->|Yes| D[Proceed with ripening/induction]:::action C -->|No| E[Perform BPP or ultrasound]:::action E --> F{Normal?}:::decision F -->|Yes| D F -->|No| G[Delay induction, investigate further]:::urgent ```