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What does cst means
This is a medical case sheet. In this context, CST stands for Contraction Stress Test.
It is a test done in obstetrics (during pregnancy) to evaluate fetal well-being by monitoring the fetal heart rate in response to uterine contractions. The entry also shows:
- c/s to Dr. Reetu (AP) - Consultation sent to Dr. Reetu (Ante-Partum / Antenatal department)
- CST - Contraction Stress Test ordered
- Ky / M OBS - Likely initials of the ordering doctor / Medical Officer (Obstetrics)
The earlier entries mention pre-transfusion medications and a blood pressure threshold (>140/90 mmHg), suggesting this is an antenatal patient being monitored for a high-risk pregnancy condition such as preeclampsia.
What is that why it’s done
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"contraction stress test" fetal surveillance
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Here is a full explanation of the Contraction Stress Test (CST):
What is the CST?
The Contraction Stress Test (CST) is an antepartum (before-labor) fetal surveillance test. It monitors how the baby's heart rate responds to uterine contractions. It is done to check if the baby is getting enough oxygen through the placenta.
It was one of the earliest tests developed to assess fetal well-being, first introduced in the 1970s.
Why is it Done?
It is done to detect uteroplacental insufficiency - a condition where the placenta is not delivering enough oxygen to the baby.
During a uterine contraction, blood flow to the placenta briefly decreases. If the placenta is already not working well, even this brief dip causes the baby to become hypoxic (low oxygen), which shows up as a late deceleration (drop in fetal heart rate after a contraction). This is the warning sign the test looks for.
Specific indications:
- Suspected fetal compromise in a high-risk pregnancy (like this patient with high blood pressure / preeclampsia)
- Abnormal or non-reassuring Non-Stress Test (NST), Modified BPP, or BPP result
- Follow-up evaluation when other fetal tests are inconclusive
How is it Done?
- The mother is connected to a fetal heart rate monitor and uterine contraction monitor
- Contractions are triggered by:
- Nipple stimulation (natural method), OR
- IV oxytocin drip (called the Oxytocin Challenge Test / OCT)
- At least 3 contractions in 10 minutes must occur for evaluation
- The fetal heart rate pattern during and after contractions is analyzed
- The test takes about 40-90 minutes
How is the Result Interpreted?
| Result | Meaning |
|---|---|
| Negative (Normal) | No late decelerations - baby is coping well, placenta is working fine |
| Positive (Abnormal) | Late decelerations with contractions - baby may be in distress |
| Equivocal | Variable decelerations - may suggest cord compression, needs further testing |
A negative CST is very reassuring - the chance of fetal loss within 1 week is only about 0.03%, making it the most sensitive antenatal surveillance test.
Why Was It Ordered for This Patient?
This patient likely has preeclampsia (high BP >140/90 mmHg is mentioned in the notes, along with pre-transfusion medications). Preeclampsia causes poor placental blood flow, putting the baby at risk. The CST was ordered to check if the baby is tolerating the reduced placental function safely.
Contraindications (When NOT to Do It)
- Placenta previa
- Prior premature labor with cervical changes
- Incompetent cervix
- Classical (vertical) cesarean scar
These situations make inducing contractions risky.
- Pfenninger and Fowler's Procedures for Primary Care, p. 1153
- Creasy & Resnik's Maternal-Fetal Medicine: Principles and Practice, p. 723
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