Role of Non-Stress Test (NST) in Pregnancy
1. Assess Fetal Oxygenation and Well-Being
NST evaluates fetal heart rate (FHR) patterns in response to fetal movements.
A reactive NST suggests adequate fetal oxygenation and intact autonomic nervous system.
✅ 2. Screening Tool for Fetal Hypoxia
Early detection of chronic fetal hypoxia in at-risk pregnancies.
Helps decide whether further testing or delivery is needed.
✅ 3. Monitoring High-Risk Pregnancies
NST is commonly used in conditions such as:
Diabetes mellitus
Hypertension / preeclampsia
Fetal growth restriction (IUGR)
Post-term pregnancy (40 weeks)
Decreased fetal movements
Oligohydramnios
Multiple pregnancy
Rh isoimmunization
✅ 4. Guide Timing of Delivery
Nonreactive NST may prompt:
Biophysical profile (BPP)
Contraction stress test
Early delivery if indicated
✅ 5. Safe and Non-Invasive Monitoring
Uses external Doppler; no risk to mother or fetus.
Can be repeated frequently.
🩺 Interpretation
Reactive NST:
accelerations of fetal heart rate (15 bpm for 15 sec) within 20 minutes → Normal / reassuring
Nonreactive NST:
No adequate accelerations in 40 minutes → requires further evaluation.
⭐ Key Points for Exams
NST becomes reliable after 32 weeks (fetal autonomic maturity).
First test done in most high-risk pregnancies.
Part of biophysical profile.
