hi I'm Sarah and this is a video about the stages of labor so labor refers to the delivery of a baby this does not happen by means of a stork but actually describes several stages of hard work endured by the mother until the baby is delivered so this occurs between 37 and 42 weeks when the fetus is full term in some cases labor may occur before 37 weeks and this is referred to as preterm labor It is divided into three stages. We've got stage one where the cervix opens to full dilatation allowing the head to pass through. We've got stage two which is from full dilatation of the cervix to delivery of the fetus and stage three which involves delivery of the placenta.
Great so first let's have a look at how labor begins. Okay so at the end of the third trimester The cervix is being stretched by the baby due to release of certain factors. The stretching of the cervix sends signals to the brain which in turn releases oxytocin.
Oxytocin then stimulates uterine contractions. At the same time the placenta releases prostaglandins which also stimulate uterine contractions. These uterine contractions force the cervix to stretch even more and therefore stimulating further contractions in a positive feedback loop.
Initially, these contractions will be mild and irregular, and are referred to as Braxton Hicks contractions, or false labour pains. These contractions may be accompanied by the show of labour. This refers to the mucus plug, which covers the cervical os.
It protects the cervix and prevents bacteria from entering the uterus. It is supported by oestrogen, so when this starts to decline at the end of the pregnancy, The mucus plug will fall and present as a pinkish discharge referred to as the show of labour. The uterine contractions may also result in rupture of the amniotic membranes and the mother will present with a sudden gush of fluid. These will both stimulate contractions further until we get to the first stage of labour. So essentially the first stage of labour refers to the process by which the cervix becomes fully dilated.
that is dilated up to 10 centimeters as we can see in the pictures over here now the first stage of labor is divided into two we have the latent phase and the active phase during the latent phase the cervix is slowly dilating up to four centimeters and we have irregular uterine contractions this phase can take up to several hours then we've got the active phase where we have painful regular contractions now which result in the cervix becoming fully dilated great over here we have another set of diagrams showing us the progression of the cervix so we talk about effacement and dilatation so essentially effacement refers to the thickness of the cervix while dilatation refers to how open the cervical loss is so here we can see that the cervix is thick and closed therefore not a face and not dilated then the cervix first becomes fully effaced as it is ripening and preparing for labor and slowly starts dilating and here it is one centimeter dilated in the next diagram it is up to five centimeters dilated so since over here the dilatation is beyond four centimeters we are in the active phase of the first stage and then the cervix becomes fully dilated ready to proceed to the second stage Some important points I'd like to add here. So essentially, this process is slower in nulliparous women, with the active stage occurring around 1 cm per hour versus 2 cm per hour in multiparous women. In general, the duration of the active stage is usually less than 12 hours. During the first stage of labour, the membranes will rupture, unless they haven't already ruptured.
Okay, good, so next we've got the second stage. and this refers to the period from full dilatation of the cervix till the baby is delivered this is also divided into two stages so we've got the passive stage and the active stage during the passive stage we are allowing for the scent of the fetal head until it reaches the pelvic floor and the woman experiences the desire to push The active stage is when the mother is actively pushing. Now the second stage essentially is the process by which the baby must navigate through the maternal pelvis.
And we have three factors which determine the progress, which we call the three P's. We've got the powers, the passage, and the passenger. And we're going to look into each of these. So first up, the powers just refer to the strength of the uterine contractions.
we should have around four to five strong contractions in 10 minutes next we've got the passage and this is mainly referring to the maternal pelvis so let us take a look at the anatomy of the pelvis so the pelvis essentially has three principal planes we've got the inlet mid cavity and the outlet so first the inlet this is where the passage of the fetal head down the pelvis starts off it is bounded anteriorly by the symphysis pubis and crest laterally by the pectineal lines and posteriorly by the base of the sacrum and sacral promontory as we can see here the inlet has a transverse diameter of 13 centimeters an oblique diameter of 12 centimeters and an anterior posterior diameter of 11 centimeters so what i'm going to do here is start jotting these diameters down and you'll see why later on so for the pelvic inlet we said that the transverse diameter was 13 centimeters oblique diameter 12 centimeters and anthropocene diameter 11 centimeters so next moving on to the mid cavity so as we can see the diameters have changed now and we've got a transverse diameter of 12 centimeters an oblique diameter of 13 centimeters and an anterior posterior diameter of 12 centimeters and we're going to jot them down in the table again then we have the pelvic outlet so bounded anteriorly by the pubic arch laterally the ischial tuberosities and ischial spines and posteriorly by the coccyx now these skill spines are palpable vaginally and we use them as landmarks to assess the station but what is the station so the station refers to the descent of the fetal head and is measured according to the position relative to the ischial spines. So basically station zero is when the head is at the level of the spines. Station plus two is when the head is two centimeters below and minus two is when the head is two centimeters above as we can see over here.
Great so back to our pelvic outlet we've got a transverse diameter of 11 centimeters, an oblique diameter of 12 centimeters and an anterior-posterior diameter of 13 centimeters. good so here they are again written our table now obviously to make delivery easier we want the fetal head to pass through the largest space available in the pelvis and as we can see over here the largest diameters are the transverse diameter of the pelvic inlet the oblique diameter of the mid cavity and the anterior posterior diameter of the pelvic outlet so we shall be seeing how the head shall be rotating accordingly to fit these largest diameters so keep this in mind we're going to refer back to this great so next we're going to move on to the passenger so here of course we're talking about the characteristics regarding the baby and essentially we have three which we need to consider and these are the size of the head the fetal attitude and the position so let's start off with the head so here we need to go back to the anatomy again so here we have the fetal skull So starting off with the bones, we have the two frontal bones, the two parietal bones and the occipital bone. Now as you can see the bones are not fused yet, but there are spaces in between and these are called the sutures and the fontanelles. So between the frontal bones we have the frontal suture, between the frontal bones and the parietal bones we have the coronal suture, between the two parietal bones we have the sagittal suture, and between the parietal and occipital bones we have the lamdoid suture. Now the space over here is referred to as the anterior fontanelle or the bregma and here we've got the posterior fontanelle also referred to as the occiput.
Good so essentially because of these spaces between the bones the head can be compressed as the bones come closer together and sometimes also overlap and this is referred to as molding as you can see in these diagrams. Increased pressure can also result in localized swelling, which is referred to as kaput. Good, so next we're going to talk about the fetal attitude.
Now this is referring to the degree of flexion of the head on the neck. So ideally the head is completely flexed, as we can see in this picture. Why? Because it gives us the smallest possible presenting diameter of the fetal skull, which is 9.5 cm.
This is also called the vertex presentation. If the head is not flexed, which we call deflexed, we've got a larger diameter of 11.5 centimeters if the head is extended with a brow presentation we have a 13 centimeter diameter then if the head is hyper extended we get a face presentation with a diameter of 9.5 centimeters so on my task face presentation is also a good feet latitude because it also has a 9.5 centimeter diameter The problem is that as we're going to see soon when the head is being delivered one of the maneuvers used to exit out of the pelvis is extension and in this case since the head is fully extended there is no further extension which can take place to aid delivery hence creating problems. Okay so lastly we've got position so here we're referring to the rotation of the head on the neck and essentially what positions the head is taking while maneuvering through the pelvis. So essentially we want the smallest diameter of the head to pass through the largest diameter of the pelvis.
So let's look at the table again showing the dimensions of the pelvis. So the pelvic inlet was largest in its transverse diameter. Therefore as we can see here the head is entering the pelvis in a transverse position which we call occipitotransverse position.
in the mid cavity which is largest in its oblique diameter we have the head rotating then in the pelvic outlet having its largest diameter in the anterior posterior plane the head has rotated 90 degrees in an occipital anterior position to exit the pelvic outlet great so now that we have understood the three p's we can move on to delivery of the head So essentially first we have flexion of the head giving us that small 9.5 cm diameter with the vertex presentation. The head descends into the mid cavity. As we said then it starts rotating so that once the head has reached the pelvic outlet it has turned by 90 degrees and now lies in an occipital anterior position.
Then the head is delivered through extension of the head on the neck. Once the head is out it returns and rotates by 90 degrees back to its original position and this is called restitution this is done to help delivery of the shoulders so they do they too can enter the inlet of the pelvis to its largest diameter so another set of pictures over here so first we have delivery of the anterior shoulder then the posterior shoulder until the entire body an umbilical cord is delivered and that is the end of the second stage so now we have the third stage which refers to the delivery of the placenta it usually lasts about 15 minutes and normal blood loss is up to 500 mils and that is the end of labor i hope that this video was helpful thank you