NST test

fetal heart rate monitoring

What is cardiotocography/Non-stress test for?

Checking the heart rate of the fetus is a long-known examination procedure in obstetrics. In the perinatal period, the normal fetal heart rate is 110-160/min. Cardiotocography (CTG) is the detection of the heart rate of the fetus as a function of time at the same time as the contraction of the uterus and the movement of the fetus. If the cardiotocography examination is performed in a state of rest, in the case of labor that has not started, then we are talking about NST, Non-stress test examination. During this, we detect the heart rate of the fetus, possible uterine activity (contractions of the uterine muscles), fetal movements, and the machine displays the result graphically on a strip of paper.

During the examination, we evaluate moment-to-moment changes in heart rate (this is called oscillation, i.e. a sawtooth-like pattern), periodic changes (accelerations, decelerations) and permanent heart rate deviations. With the help of the examination procedure, we can obtain essential information regarding the state of the fetus inside the womb. In a state of oxygen deficiency, we see characteristic deviations on the NST, for example: a "narrowing" of the oscillation, i.e. a decrease in the degree of the sawtooth-like pattern, a temporary or, in more severe cases, a permanent slowing of the heart rate. The examination therefore enables the early recognition of fetal danger conditions not only during childbirth, but also during pregnancy.

What is the course of the NST test, how long does it take?

The NST test is usually performed in the last third of pregnancy, i.e. in the third trimester. During prenatal care, starting from the 36th week of pregnancy, it is necessary to perform the test once a week, after the 40th week, it is recommended to perform the examination daily. In the case of certain pregnancy conditions (e.g. high blood pressure, diabetes, intrauterine growth retardation of the fetus), it may be necessary to perform NST tests in the earlier stages of pregnancy and with greater frequency.

The examination usually lasts 20 minutes, is completely safe, does not cause pain or danger.

It is essential that the fetus is "active" during the examination, i.e. it moves intensively, this makes it possible for us to assess the changes in its heart rate due to its movements.

Before the NST examination, it is advisable to consume plenty of liquid and food with a high carbohydrate content (chocolate, sugar), as these have a stimulating effect on the activity of the fetus.

What is a biophysical profile?

Supplementing the NST examination with fetal ultrasound and doppler examination is called a biophysical profile examination, which by monitoring the fetal breathing movements, tone and amniotic fluid volume can predict any fetal danger state more sensitively than the NST examination alone.