What Is Electronic Fetal Monitoring?

Fetal electronic monitoring can continuously observe and record the dynamic changes of fetal heart rate (FHR), and understand the relationship between fetal heart rate, fetal movement and contractions, and estimate the intrauterine safety of the fetus.

Fetal electronic monitoring

Fetal electronic monitoring can continuously observe and record the dynamic changes of fetal heart rate (FHR), and understand the relationship between fetal heart rate, fetal movement and contractions, and estimate the intrauterine safety of the fetus.

Chinese name

Fetal electronic monitoring

Foreign name

NST, OCT, CST

You can use a stethoscope or a Doppler fetal heart auscultation device during uterine contractions. The fetal heart rate should be between 110 and 160 bpm. Excluding the effects of drugs, infections, or operations during labor, fetal heart rate 160 bpm is tachycardia, such as 180bpm is severe tachycardia, 120bpm is bradycardia, 100 bpm is severe bradycardia. Fetal heart deceleration associated with contractions can also be found with a stethoscope. Use the stethoscope to place the fetal heart at the clearest place. Continuously auscultate before, during, and after the contraction. The contraction can be heard 3 times. For example, deceleration after contractions, or decelerations with uncertain relationship with contractions, are late or variable decelerations. Most large and fast recovery decelerations are mostly variable decelerations. s appears, the amplitude is small, about 10-20 bpm, 30 seconds after the end of the contraction can return to the baseline. If the deceleration synchronized with the contractions is an early deceleration, during auscultation, due to factors such as increased intrauterine pressure or abdominal muscles caused by the contractions, the fetal heart signal disappears, so the early deceleration cannot be heard. Closely related to fetal hypoxia is late deceleration and variable deceleration.

1) Baseline Heart Rate (BFHR):

FHR was recorded for 10 minutes without fetal movement and contractions. Normal FHR is 120-160bpm; FHR> 160bpm is tachycardia , <120bpm is bradycardia ; baseline oscillations of fetal heart rate include the amplitude and frequency of variation of fetal heart rate. The variation amplitude is the range of fetal heart rate fluctuation, generally 10-25bpm. The frequency of variation is the number of fetal heart rate fluctuations within 1 minute, normal> = 6 times.

2) Transient fetal heart rate changes:

Refers to the relationship between fetal heart rate and uterine contraction.

Acceleration: refers to a temporary increase in fetal heart rate baseline of more than 15 bpm with a contraction for duration> 15 seconds. This is a good fetal performance and may be caused by compression of the fetal trunk or umbilical vein.

Deceleration: refers to the temporary decrease in fetal heart rate that occurs with contractions. There are three types: a Early deceleration (ED) FHR deceleration starts almost at the same time as contraction. The lowest point of FHR is at the peak of contraction, with a decrease of <50bpm, short duration, and rapid recovery. It is generally considered that the late stage of the first stage of labor is caused by the pressure of the fetal head during contractions; b Late deceleration (LD): FHR deceleration begins to appear after the peak of contractions, and the rate of slow decline is less than 50 bpm, which lasts for a long time and recovers. slow. It is generally believed that placental dysfunction is the manifestation of fetal hypoxia; c variable deceleration (VD): FHR mutations are irregular in shape, and there is no constant relationship between deceleration and uterine contractions, and the duration varies, with a decline of> 70 bpm, and recovery is rapid. Generally believed that the umbilical cord is caused by compression.

1) No stress test

(Non-stress test, NST)

Through the change of fetal heart rate during fetal movement, understand the fetal reserve capacity. FHR acceleration during fetal movement> = 15bpm, duration> = 15 seconds is reactive; if there is no fetal heart rate acceleration during fetal movement, fetal heart rate acceleration <15bpm during fetal movement, duration <15 seconds is non-responsive, it should be reviewed after one week . High-risk pregnancy is reviewed twice a week. This test is a screening test for the oxytocin challenge test.

2) Oxytocin Stimulation Test

(Oxytocin challenge test, OCT)

Also known as the contraction stress test (CST), the change in fetal heart rate during contractions within 20 minutes is observed through oxytocin-induced contractions, and the changes in the placental transient hypoxia load are measured to determine the fetal reserve capacity. . If there are more than three consecutive decelerations within 10 minutes, the baseline fetal heart rate variability is reduced, and no acceleration of fetal heart rate after fetal movement is OCT positive, indicating that the placental function is impaired; if there is no late deceleration of fetal heart rate, the fetal heart rate is accelerated after fetal movement OCT negative, suggesting that the placenta is functioning well and there is no risk of death within one week.