Labor Stage 1: Fetal Heart Rate Tracing

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.