# Contraction Stress Test

> Oxytocin challenge method, interpretation and contraindications of the contraction stress test, for NEET-PG Obstetrics and Gynaecology preparation.

- Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/contraction-stress-test
- Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Williams Obstetrics; Dutta's Textbook of Obstetrics; ACOG Practice Bulletins on Antepartum Fetal Surveillance
- How to cite: "Contraction Stress Test", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/contraction-stress-test

## Direct answer

The contraction stress test is an antenatal assessment of fetal reserve that records fetal heart rate during oxytocin-induced or spontaneous uterine contractions. A negative result, with no late decelerations, is highly reassuring, while late decelerations after half or more of contractions form a positive test that suggests fetal compromise. It is contraindicated in placenta praevia, preterm labour and previous classical caesarean section.

## What you must remember

- **Purpose:** assesses uteroplacental reserve by showing whether the fetal heart tolerates contractions.
- **Adequate test:** three contractions within ten minutes are needed for a valid result.
- **Negative test:** no late decelerations, with a high negative predictive value for fetal wellbeing.
- **Positive test:** late decelerations after 50 per cent or more of contractions, suggesting uteroplacental insufficiency.
- **Equivocal test:** intermittent late decelerations after fewer than half of contractions, or suspicious patterns, which need repeat assessment.
- **Hyperstimulation:** more than five contractions in ten minutes, managed by stopping the oxytocin and considering a tocolytic.
- **Second-line role:** performed when the non-stress test is non-reactive, because it needs oxytocin and carries hyperstimulation risk.
- **Contraindications:** placenta praevia, preterm labour and previous classical caesarean or other major uterine surgery.

## How the oxytocin challenge is run and read

The test is run in a monitored setting, with the woman ready for caesarean delivery if the trace deteriorates.

1. **Preparation:** Confirm a cephalic singleton with the placenta away from the os, since placenta praevia excludes the test. Obtain consent and place the fetal monitor.
2. **Baseline trace:** Record a baseline and confirm normal variability and accelerations before any oxytocin is started. The baseline is documented before oxytocin, since later changes are judged against it.
3. **Oxytocin titration:** Start a low-dose infusion and increase it stepwise every 15 to 20 minutes until adequate contractions appear, meaning three within ten minutes.
4. **Reading the trace:** Late decelerations begin after the contraction peaks and recover only after it ends. Count the proportion of contractions that show them.
5. **Stopping rules:** Stop the infusion at once for hyperstimulation, persistent late decelerations or fetal distress, and reposition the woman.
6. **Acting on the result:** A negative test allows continued surveillance, while a positive test prompts delivery planning according to gestation and cervical status. Document the result and the time, so the next team can compare traces.

## Traps in fetal surveillance

Surveillance questions often test which test comes first and when the oxytocin test must be abandoned.

- **Trap:** Performing the test after a previous classical caesarean — **Correct:** the uterine scar carries rupture risk under oxytocin, so a non-stress test or biophysical profile is used.
- **Trap:** Calling the test positive after a single late deceleration — **Correct:** positivity requires late decelerations with half or more of the contractions.
- **Trap:** Continuing oxytocin during tachysystole — **Correct:** stop the infusion, reposition the woman and consider a tocolytic.
- **Trap:** Choosing the contraction stress test as the first-line test — **Correct:** the non-stress test comes first, and the oxytocin test is reserved for a non-reactive result.

## Frequently asked questions

### What makes a contraction stress test positive?

A contraction stress test is positive when late decelerations recur after half or more of the contractions, which suggests uteroplacental insufficiency. A positive test prompts urgent obstetric review and delivery planning according to gestation and fetal condition.

### How many contractions are needed for an adequate contraction stress test?

An adequate contraction stress test needs three contractions within a ten-minute window. Fewer contractions make the test unsatisfactory, and it is repeated after the oxytocin dose is adjusted.

### When is a contraction stress test contraindicated?

A contraction stress test is contraindicated in placenta praevia, preterm labour and a previous classical caesarean or other major uterine surgery. Uterine contractions in these settings risk bleeding or uterine rupture.

### Why has the contraction stress test been largely replaced?

The contraction stress test has been largely replaced by the non-stress test and the biophysical profile, which are non-invasive and need no oxytocin. The oxytocin test carries a risk of hyperstimulation, so it is reserved for selected cases.