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Non-Stress Test – Clinic NOVA Varna
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Non-Stress Test

Non-Stress Test in Nova Clinic
The Non-Stress Test (NST) offered by Nova Clinic is a non-invasive method in obstetrics used for screening the foetal heart rate by using an obstetric monitor, without subjecting the foetus to additional stress. Indications: The test is most commonly used in the event of risky pregnancy, when there is a risk of placental insufficiency and impaired supply of oxygen and nutrients to the foetus. NST may be applied in the following cases:

reduced or lacking movements of the foetus;
small or slowly developing foetus;
the mother suffers from diabetes mellitus /which has occurred during pregnancy or before that/;
high blood pressure of the mother, preeclampsia;
impaired function of the thyroid gland;
multiple pregnancy;
preterm birth or case history of preterm birth;
overdue pregnancy;
case history of former abortions or stillbirth;
advanced maternal age;
after amniocentesis;
changes in the laboratory test results.

Contraindications: The test is non-invasive and harmless. It can be applied both during pregnancy and during labour. Technique of application: NST is usually performed after the 26-28 week of gestation. The duration of the examination is at least 20 minutes. Two belts are positioned at the front abdominal wall of the pregnant woman. One of them has a sensor for recording the foetal heart rate (placed at the position corresponding to the foetus’s back) and the other one records the uterine contractions. When she feels the foetus is moving, the pregnant women should press a button, which is used to find connection between the acceleration of the heart rate and the movement of the foetus. The sensors are connected to the obstetric monitor. The recording is printed on paper in two channels – the first one reflects the foetal heart rate and the second one – the uterine contractions.


Reactive NST – there is adequate increase in the foetal heart rate as a result of its movements – at least two accelerations for 20 minutes. The foetal heart rate is within the range of 120-160 beats per minute. Because uterine contractions act as a stress factor on the foetus, it is possible to detect early deceleration during contractions /they are observed in about one third of the births. These are slowdowns of the foetal heart rate to no less than 120-100 beats/minute, where the start coincides with the start of the uterine contraction and the end – with the end of the contraction.

Non-reactive NST – this is a test that does not meet the conditions described above. It does not necessarily mean there is any pathology. For example, it is possible that the foetus fell asleep during the test, which may be the cause for its decreased reactivity.
When the uterine-placental blood circulation is impaired, the foetus is in a state of hypoxia and its heart rate and compensatory possibilities are impaired. The reactivity is reduced, late decelerations are observed – their start is after the start of the uterine contraction and their end is after the end of the contraction and the peak of deceleration does not coincided with the peak of the contraction. During the late decelerations, the foetal heart rate falls to under 100 beats/minute. Often, during the periods between the deceleration, foetal tachycardia is registered (heart rate over 160 beats/minute).

If the result from the NST deviates from the norms, further screening is necessary:
repeating the non-stress test;
assessment of the biophysical profile of the foetus – it is done based on 5 indicators – reactivity of the foetus based on NST and ultrasound examination of the respiratory movements, the active movements and the foetal tone, as well as identification of the volume of the amniotic fluid;
performing a stress test (functional oxytocin test) – uterine contractions are provoked with oxytocin and the reactivity of the foetus is examined again.
Price: BGN 10