Labor Stage 1: Normal and Abnormal Labor

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.

    00:30 We can further divide Stage 1 labor into the latent phase, which is the onset of contractions that continue until the cervix is about 4 to 6 centimeters dilated, and the active phase, which is from 6 centimeters dilated to 10 centimeters dilated.

    00:45 Now, we have some parameters that we considered to be normal for the first stage of labor.

    00:51 For primiparous, well, I mean in latent labor, we expect that to last under 20 hours, for a multiparous, we expected it to last under 14 hours.

    01:01 In the active phase we expect the cervix to change 1.2 centimeters per hour for out first time moms.

    01:07 And 1.5 centimeters per hour for our multiparous moms.

    01:11 So we have an abnormal first stage labor.

    01:16 What causes that? Well, when we think of the 3 P's.

    01:18 Power, Passenger and Pelvis.

    01:22 With power we're talking about the strength of contractions.

    01:27 Now how do we measure the strength of the contractions.

    01:30 Typically in labor our moms are going to have a monitor on that tells us them externally how often they are contracting.

    01:36 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.

    01:56 We expect it to be 180 to 220 Montevideo units to say the contractions are adequate.

    02:02 If those contractions are not adequate, we're going to start a medication called Pitocin.

    02:08 This is a synthetic form of oxytocin and this makes the contractions stronger.

    02:12 Now our next P is passenger.

    02:17 So what can go wrong with our passenger to make the first stage of labor abnormal.

    02:22 Well we could have malrepresentation of our passenger such as a breech presentation, a face presentation or brow presentation.

    02:28 That will prevent the passenger from coming down the pelvis.

    02:31 Or the passenger could be having fetal heart rate issues.

    02:35 Now, our next P is the pelvis.

    02:38 Now there is no way to determine what type of pelvis a patient has prior to labor.

    02:45 But just to note, there are 4 different types of pelvises.

    02:49 And depending on the type of pelvis that can ease the delivery or it can make the delivery more difficult.

    02:55 So the gynecoid pelvis is one that allows the head to always rotate to also put anterior making vaginal delivery pretty easy.

    03:04 Anthropoid pelvis more common in African American women cause the fetal head to rotate to the occipit posterior position.

    03:13 While they can still have a vaginal delivery, sometimes that can be a little difficult.

    03:17 And sometimes it requires an operative vaginal delivery to get those last little maneuvers to have the fetal head go underneath the pubic symphysis.

    03:24 The platypeloid pelvis will cause the fetal head to be in a transverse position.

    03:30 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.

    03:41 Remember that the fetal pelvis is largest at 10 centimeters at it's largest point.

    03:46 A transverse presentation is not going to be able to be pass through the pelvis.

    03:51 And an android pelvis is more like a guy's pelvis and that is heart shaped.

    03:57 And in this type of presentation the fetal head has difficulty even engaging.

    About the Lecture

    The lecture Labor Stage 1: Normal and Abnormal Labor by Veronica Gillispie, MD, FACOG is from the course Intrapartum Care. It contains the following chapters:

    • First Stage of Labor
    • Stage 1 – Normal Labor
    • Stage 1 – Abnormal Labor

    Included Quiz Questions

    1. If external intrauterine pressure measurement is insufficient, an intrauterine catheter should be placed.
    2. She should be started on Pitocin to increase the frequency of her contractions.
    3. She should be given a cervical ripening agent to soften the cervix.
    4. She should be managed expectantly for spontaneous vaginal delivery with no further intervention.
    5. She should go for a cesarean section.
    1. Evaluate for fetal malpresentation
    2. Start Pitocin to increase the strength of her contractions
    3. Start Pitocin to increase the frequency of her contractions
    4. Vacuum-assisted delivery to help the baby descend into the pelvis
    5. Administer a cervical ripening agent to soften the cervix
    1. Gynecoid pelvis
    2. Anthropoid pelvis
    3. Platypelloid pelvis
    4. Android pelvis
    5. Cuboid pelvis
    1. Anterior occiput
    2. Posterior occiput
    3. Transverse anterior
    4. Transverse posterior
    5. Right anterior transverse

    Author of lecture Labor Stage 1: Normal and Abnormal Labor

     Veronica Gillispie, MD, FACOG

    Veronica Gillispie, MD, FACOG

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    By Solomon T. on 22. February 2021 for Labor Stage 1: Normal and Abnormal Labor

    well explained and detailed content and structure for easy understanding and memorization

    I Really liked it
    By ANDRES R. on 09. February 2017 for Labor Stage 1: Normal and Abnormal Labor

    I Really liked it. The example you gave with the wedding was perfect, I will never forget it.