Labor Stage 1: Normal and Abnormal Labor

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.