Labor Stage 1: Fetal Heart Rate Tracing

by Veronica Gillispie, MD, FACOG

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    00:01 Now let's discuss the interpretation of fetal heart rate tracings.

    00:06 So let's go over some terminology and some nomenclature.

    00:09 When we talk about the fetal heart rate tracing, we talk about the baseline, the variability and accelerations.

    00:17 When we talk about contraction, the bottom part of this example we discuss if the contractions are normal and what tachysystole means.

    00:26 Let's start with baseline.

    00:28 So a normal baseline is between 110 beats to a 160 beats per minute.

    00:34 And this is for the fetal heart rate.

    00:37 Tachycardia is considered to be 160 beats per minute sustained for a 10 minute time frame.

    00:44 And bradycardia is considered to be less than 100 beats per minute when it's sustained for a 10 minute time frame.

    00:52 So variability talks about the ability of the fetal heart rate to change above or below baseline.

    00:59 When the variability is absent that means there's no change in the baseline.

    01:04 When it's minimal, it means it's less than 5 beats per minute.

    01:08 Moderate is 6 to 25 beats per minute.

    01:11 And marked is greater than 25 beats per minute.

    01:14 In our example here, we would call this moderate variability.

    01:19 Now when we discuss accelerations, we divide that to before 32 weeks gestation and after 32 gestation.

    01:27 After 32 weeks gestation, we expect to see an increase in the fetal heart rate by 15 beats per minute for 15 seconds over a 2 minute tracing.

    01:37 Before 32 weeks, normal accelerations consist of an increase in the fetal heart rate by 10 beats per minute for 10 seconds over a 2 minute tracing.

    01:49 Now, contractions.

    01:52 A normal amount of contractions are 5 or less contractions in a 10 minute time frame.

    01:58 Uterine tachysystole means greater than 5 contractions in 10 minutes.

    02:03 Now there's something called Montevideo Units.

    02:07 When normally a patient is monotronant labor they have an external fetal monotron.

    02:12 Because it sits at top of the abdomen, it only tells us how often a patient is contracting.

    02:18 It doesn't tell us how strong those contractions are.

    02:22 Within intrauterine pressure catheter we're able to determine the strength of the contractions.

    02:27 Now how do we do this.

    02:29 We take a 10 minute strip or a 10 minute tracing.

    02:33 We look at the contractions during that time and we measure the area under the curve.

    02:38 Now a normal amount of contraction or strength of contraction would be between 180 to 220 Montevideo units.

    02:48 That's considered to be adequate contractions to allow labor to progress.

    02:54 Now that we've talked about the fetal heart rate tracing and some of the terminology, let's talk about the nomenclature.

    03:01 So why do we even look at fetal heart tracing.

    03:04 Well, fetal heart rate tracing provides an information to us to tell us about the current acid-base status of the fetus.

    03:11 Now we have 3 categories.

    03:13 Category 1 which is normal.

    03:16 Category 2 which can be indeterminate.

    03:18 And Category 3 which we consider abnormal.

    03:21 Let's see what makes each of those categories.

    03:26 So a category 1 tracing.

    03:28 In order for a tracing to be considered Category 1, such as this one, the fetal heart rate has to be between 110 to 160 beats per minute.

    03:38 There must be moderate variability.

    03:40 And there are no late or variable decelerations.

    03:46 Now, a Category 2 tracing.

    03:49 Again this is indeterminate to determine the acid-base status of our fetus.

    03:56 So the fetal heart rate can be between 110 to 160 beats per minute.

    04:01 But it can also be 100 beats per minute which remember that means bradycardia.

    04:06 But variability must be present.

    04:09 It can be greater than 160 beats per minute which again that means tachycardia.

    04:14 But again variability must be present.

    04:19 As far as the variability it can be minimal or moderate.

    04:23 Or if it is absent, such as in this case, there can be no late or variable deceleration for it to be considered a Category 2 tracing.

    04:33 Acceleration should be present.

    04:37 And if there are decelerations which again those can be late or variable, they can be present if there is minimal or moderate variability present.

    04:49 Now, Category 3 tracing.

    04:51 This is considered abnormal.

    04:52 And this would mean that the acid base fetal status is abnormal.

    05:00 So, Category 3.

    05:01 What makes a Category 3 tracing.

    05:03 As far is variability it is absent with late or variable decelerations.

    05:08 Such as in this tracing.

    05:12 There can be bradycardia which again is less than a 100 beats per minute.

    05:16 Or something called as Sinusoidal Pattern.

    05:18 You also see this called a see-saw pattern.

    05:20 And that actually shows fetal anemia.

    05:24 Now let's talk about the different types of decelerations that we can see on a fetal heart rate tracing.

    05:29 We have early decelerations.

    05:31 These decelerations particularly mirror the contractions and these are physiologic.

    05:36 They are due to the head compression and due to stimulation of the vagus nerve.

    05:40 Because they are physiologic, there's nothing that we need to do about them.

    05:46 Variable decelerations, you can see there's a sharp decline in the fetal heart decline and there's a sharp incline back to the baseline.

    05:55 Variable decelerations are due to cord compression.

    05:59 Now, they can be released by doing amino infusion which is placing fluid inside the uterus through the intrauterine pressure catheter.

    06:07 That allows the fetus to get off of the cord and to release these variable decelerations.

    06:13 Now late decelerations are little bit more ominous.

    06:16 These are due to the utero-placental insufficiency.

    06:20 These we do have to address and we do want to correct.

    06:23 So how do we address them.

    06:25 1. We give oxygen to the moms so there's more oxygen going to the fetus.

    06:29 2. If we are given pitocin to make contractions happen, we want to stop the pitocin.

    06:35 3. We want to give IV fluids because that will allow more fluid to go to the placenta.

    06:41 And then 4. We want to commonly place the patient in left lateral decubitus.

    06:46 So that means we roll them on to the left side.

    06:49 That will rotate the uterus off of the inferior vena cava.

    06:53 So we have increased venous return to the placenta.

    06:58 Now let's take a case.

    07:00 You are called to the bedside of a 23 year old Gravida 1 Para 0 female who was admitted in active labor.

    07:09 On her most recent cervical exam she was 5/90 and -1.

    07:14 She received an epidural approximately 10 minutes ago.

    07:18 Her fetal heart rate tracing which was Category 1, is now shown to be this.

    07:24 How would you describe this tracing? What nomenclature would you use? Now would you say that, A. The patient is having early decelerations, most likely from rapid cervical change.

    07:42 B. Patient is having late decelerations most likely from rapid cervical change.

    07:48 C. Patient is having late decelerations most likely from hypotension related to recent epidural placement.

    07:55 or D. Patient demonstrates at Category 1 fetal heart tracing.

    08:02 The answer is C.

    08:03 We would describe this fetal heart rate tracing as a Category 3.

    08:07 We can see that the patient is having a large late deceleration.

    08:11 Now it's important to remember that when the epidural is placed, a lot of times moms will suffer from hypotension.

    08:17 This causes utero-placental insufficiency.

    08:20 And the fetus will compensate by having late decelerations.

    About the Lecture

    The lecture Labor Stage 1: Fetal Heart Rate Tracing by Veronica Gillispie, MD, FACOG is from the course Intrapartum Care. It contains the following chapters:

    • Fetal Heart Rate Tracing
    • Fetal Heart Rate Tracing – Categories

    Included Quiz Questions

    1. 110-160 beats per minute
    2. 100-150 beats per minute
    3. 130-160 beats per minute
    4. 100-130 beats per minute
    5. 135-145 beats per minute
    1. An increase in fetal heart rate by 15 beats per minute for 15 seconds over a 2-minute tracing
    2. An increase in fetal heart rate by 10 beats per minute for 15 seconds over a 2-minute tracing
    3. An increase in fetal heart rate by 15 beats per minute for 10 seconds over a 2-minute tracing
    4. An increase in fetal heart rate by 10 beats per minute for 10 seconds over a 20-minute tracing
    5. An increase in fetal heart rate by 20 beats per minute for 15 seconds over a 20-minute tracing
    1. Category 3, patient has tachysystole and the Pitocin must be stopped
    2. Category 2, patient has tachysystole and the Pitocin should be stopped
    3. Category 1, it is ok to continue the course of management as is
    4. Category 2, the patient is likely not taking in deep breaths due to pain from regular contractions and should get oxygen supplementation
    5. Category 2, the patient should be rotated to relieve cord compression
    1. Baseline 135 with moderate variability and recurrent late decelerations over a 20-minute strip.
    2. Baseline 145 with no variability and late decelerations over a 20-minute strip.
    3. Baseline 165 with no variability and variable decelerations over a 20-minute strip.
    4. Baseline 180 with no variability and no accelerations over a 20-minute strip.
    5. Baseline 80 with no variability and a few late decelerations over a 20-minute strip.
    1. It indicates fetal anemia
    2. It is a sign of maternal polycythemia
    3. It indicates cord compression
    4. It indicates head compression of the fetus
    5. It is a sign of fetal death
    1. Physiologic response to fetal head compression after rapid descent of the fetal head in the pelvis
    2. Cord compression due to prolapse of the cord
    3. Uteroplacental insufficiency due to maternal intravascular volume depletion
    4. Fetal anemia resulting in a sinusoidal fetal heart tracing pattern
    5. Fetal bradycardia due to uteroplacental insufficiency
    1. It represents cord compression
    2. It indicates fetal anemia
    3. It is a category 3 strip
    4. It requires immediate intervention
    5. It suggests abnormal fetal acid/base status
    1. It is defined as greater than 5 contractions over 10 minutes
    2. It can only be determined by an internal uterine pressure catheter
    3. It can be monitored without intervention as long as the fetal heart tracing is not Category 3
    4. It is defined as over 10 contractions in 10 minutes
    5. It is defined as overlapping contractions without any uterine relaxation in between contractions

    Author of lecture Labor Stage 1: Fetal Heart Rate Tracing

     Veronica Gillispie, MD, FACOG

    Veronica Gillispie, MD, FACOG

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    Great Lecture!
    By Pharlin N. on 24. October 2020 for Labor Stage 1: Fetal Heart Rate Tracing

    Thanks so much for making this complex topic clear and simple.