Labor Stage 1: Fetal Heart Rate Tracing

by Veronica Gillispie, MD, FACOG

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    00:01 Now let's discuss the first stage of labor.

    00:05 So in review of all of our stages of labor, let's remember that Stage 1 starts from onset of labor until 10 centimeters dilated.

    00:13 Stage 2 is 10 centimeters dilated until the delivery of the infant.

    00:17 And Stage 3 starts with the delivery of the infant and ends with delivery of the placenta.

    00:22 So in Stage 1 we have contractions that are causing cervical change and they are also causing the fetus to descend in the pelvis.

    00:31 We can further divide Stage 1 into latent labor which is onset of contractions until 4 centimeters dilated.

    00:38 And into the active phase.

    00:40 This is from 4 centimeters dilated to 10 centimeters dilated.

    00:45 Now let's consider normal.

    00:47 For our primiparous first time moms, the latent labor can last to 6 to 11 hours.

    00:52 For multiparous 4 to 8 hours.

    00:54 In the active phase we expect the cervix to change 1.2 centimeters per hour for out first time moms.

    01:01 And 1.5 centimeters per hour for our multiparous moms.

    01:06 So we have an abnormal first stage labor.

    01:08 What causes that? Well, when we think of the 3 P's.

    01:12 Power, Passenger and Pelvis.

    01:16 With power we're talking about the strength of contractions.

    01:20 Now how do we measure the strength of the contractions.

    01:23 Typically in labor our moms are going to have a monitor on that tells us them externally how often they are contracting.

    01:30 If we want to know how strong the contractions are, we place an intrauterine pressure catheter that measures something called "The Montevideo Units." The Montevideo units are a measurement that are taken over 10 minute strip looking at all of the contractions and measuring the area under the curb.

    01:48 We expect it to be 180 to 220 Montevideo units to say the contractions are adequate.

    01:55 If those contractions are not adequate, we're going to start a medication called Pitocin.

    02:01 This is a synthetic form of oxytocin and this makes the contractions stronger.

    02:07 Now our next P is passenger.

    02:09 So what can go wrong with our passenger to make the first stage of labor abnormal.

    02:14 Well we could have malrepresentation of our passenger such as a breech presentation, a face presentation or brow presentation.

    02:22 That will prevent the passenger from coming down the pelvis.

    02:24 Or the passenger could be having fetal heart rate issues.

    02:30 Now, our next P is the pelvis.

    02:33 Now there is no way to determine what type of pelvis a patient has prior to labor.

    02:38 But just to note, there are 4 different types of pelvises.

    02:41 And depending on the type of pelvis that can ease the delivery or it can make the delivery more difficult.

    02:48 So the gynecoid pelvis is one that allows the head to always rotate to also put anterior making vaginal delivery pretty easy.

    02:57 Anthropoid pelvis more common in African American women cause the fetal head to rotate to the occipit posterior position.

    03:05 While they can still have a vaginal delivery, sometimes that can be a little difficult.

    03:09 And sometimes it requires an operative vaginal delivery to get those last little maneuvers to have the fetal head go underneath the pubic symphysis.

    03:17 The platypeloid pelvis will cause the fetal head to be in a transverse position.

    03:23 If you remember from our previous lecture, we need that fetal head to occipit anterior or occipit posterior so that only 9 and half centimeters of the fetal vertex is trying to pass through the pelvis.

    03:35 Remember that the fetal pelvis is largest at 10 centimeters at it's largest point.

    03:40 A transverse presentation is not going to be able to be pass through the pelvis.

    03:44 And an android pelvis is more like a guy's pelvis and that is heart shaped.

    03:50 And in this type of presentation the fetal head has difficulty even engaging.

    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, patient is likely not taking in deep breaths due to pain from regular contractions and should get oxygen supplementation
    5. Category 2, patient should be rotated to relieve cord compression
    1. Baseline 135 with moderate variability and variable decelerations and one late deceleration over a 20 minute strip
    2. Baseline 145 with moderate variability and no decelerations over a 20 minute strip
    3. Baseline 165 with absent variability and variable decelerations, no late decelerations or accelerations over a 20 minute strip
    4. Baseline 160 with moderate variability and accelerations over a 20 minute strip
    5. Baseline 125 with moderate variability a few early decelerations over a 20 minute strip
    1. It indicates uteroplacental insufficiency
    2. It indicates indeterminate acid/base status of the fetus
    3. It indicates cord compression
    4. It indicates head compression of the fetus
    5. It is always a sign of fetal anemia
    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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