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.