Mechanism of normal labor and the cardinal movements

The mechanism of normal labor is basically classified into three types;

1.Fetus in utero
2.The definition of the mechanism of labor
3.The cardinal movements of normal labor

1.Fetus in utero

In normal labor, the fetal position in the maternal uterus is like ;
The lie is longitudinal. The presentation is cephalic. Here the presenting part of the fetus is the vertex.
The attitude and denominator are respectively generalized flexion and extension. Also, the positions are like right occiput anterior or left occiput anterior.


What is the diameter of engagement of the pelvis?

In the inlet of the maternal pelvis, the transverse diameter is 13cm.

What is the diameter of engagement of the fetal skull?

The diameter of the fetal skull for engagement is like the sub-occipital bregmatic is 9.5 cm and the sub-occipital frontal is 10cm.


2.What is the definition of the mechanism of labor?


The mechanism of normal labor is defined as the series of movements that occur on the head, in the process of adaptation during its journey through the pelvis.

It is also defined as the series of changes in position and attitude that the presenting part has to make during its passage through the pelvis and pelvic floor during the course of labor.


3.What do you mean by cardinal movements of normal labor?


It is nothing but the entering of the fetal head into the maternal pelvic brim in normal labor. This mainly occurs through the transverse diameter and to a lesser extent through one of the oblique diameters.
Here the most common position is the left occipital anterior. As compared to the right occipital anterior it’s the commonest one as the left oblique diameter is encroached by the rectum.

The diameter of the head, engaged in the anterior posteriorly is either sub-occipital bregmatic or sub-occipital frontal. The sub-occipital bregmatic diameter and sub-occipital frontal are respectively 9.5cm and 10 cm.

Principal movements of normal labor

1.engagement during labor

In the left occipital anterior position (LOA), the vertex of the fetal head enters the pelvic brim along with the occiput. Here occiput is the denominator.

And the occiput is lying with the left iliopectineal eminence and sinciput at the right sacroiliac joint. Like that the sagittal suture of the fetus lying on the right oblique diameter of the maternal pelvis.

Engagement in ROA

In the right occipital anterior position(ROA), the vertex of the fetal head is situated in the left oblique diameter of the pelvis. And the occiput is lying in the right anterior quadrant of the maternal pelvis.

In this phase, the engaging fetal head diameter is biparietal 9.5cm. And the anterior-posterior bregmatic is also 9.5cm. Both lie on the same plane.


Primigravida and multipara


In a primigravida mother, the engagement starts before the onset of labor. But, in multipara mother, the engagement occurs in the late first stage.


2.Descent during labor

The descent is a continuous process. It is continued until there is no bony tissue obstruction.

Basically, the process of descent is slow in the first stage of labor. It is progressive during the second stage. This is concluded with the delivery of the fetus.

The factors responsible for descent are;

Contraction and retraction of the uterus
Bearing down effects
Straightening of fetal ovoid especially after rupturing of the membrane



The fetal head is flex due to the resistance. This resistance is provided by the birth canal during descent.

The factors responsible for flexion during normal labor are;
Unfolded cervix
Wall of pelvis
Pelvic floor


4.Internal rotation

In occipital lateral position, there will be anterior rotation by 2/8 that of a circle of occiput whereas in oblique, the rotation is ⅛ the of a circle placing the occiput behind symphysis pubis.


In crowing, the maximum diameters of the head stretch the vulva outlet without a recession of the head even after the contraction is over called “ crowing of the head”.



Delivery of the head takes place by extension through the “couple of force” theory. In this theory, the driving force pushes the head in a downward direction.

While the pelvic floor offers resistance in the upward and forward direction. The downward and upward force neutralizes and the forward thrust helps in extension.

The successive part of the fetal head is born through stretched vulva outlets are the vertex, brow, and face.



It is the visible passive movements of the head. it occurs mainly due to the untwisting of the neck sustained during internal rotation. Movements of restitution occur by rotating the head through 1/8th a circle in the direction opposite to the internal rotation.


8.External rotation with the internal rotation of shoulders

It is this movement of the head, visible externally due to the internal rotation of the shoulder. As the anterior shoulder rotates towards the symphysis pubis.

This process helps the fetal head to move externally through 1/8th of a circle. it occurs in the same direction as restitution. The shoulders now lie in anteroposterior diameters.


9.Expulsion or the birth of the shoulder and trunk

After the external rotation of the fetal head, the shoulders are in the anteroposterior diameter. Again descent takes place. It helps the anterior shoulder escape below the symphysis pubis.







The shoulder comes out due to the lateral flexion of the maternal spine. Like that, the posterior shoulder also escapes over the perineum. Afterward, the trunk is expelled out by lateral flexion.

About Author

I Love To Learn Everyday


  1. […] The umbilical cord is a firm connection between the mother and her fetus present in the womb. In most cases, the hole is sealed after birth. but, in some cases, they don’t join completely. As a result, the intestine, and other fatty tissues poke through the weak abdominal wall. […]

  2. […] labor, the doctor gives intravenous fluid therapy and oxygen therapy and also regularly checks the fetal […]

  3. […] occurs after delivery. Also can lead to permanent diabetes insipidus. Sometimes the placenta abruption is the main reason […]

  4. […] off to stew in pain. It takes a huge weight off my mind. I didn’t have to plan my schedule around debilitating cramps, which was nearly as impactful as not having to experience the pain itself. Of course, this is my […]

  5. I Fashion Styles says:

    Hello! I’m at work surfing around your blog from my new iphone 4! Just wanted to say I love reading your blog and look forward to all your posts! Carry on the excellent work!

  6. […] protected, in an identical manner, it will take a while in your physique to recuperate from being pregnant. But for that, you might want to transfer your […]

  7. Hairstyles says:

    Hey there! Do you know if they make any plugins to help with SEO? I’m trying to get my blog to rank for some targeted keywords but I’m not seeing very good results. If you know of any please share. Thank you!

  8. Beauty Fashion says:

    Thank you for your whole effort on this web site. My aunt really loves getting into research and it’s really obvious why. A lot of people notice all about the powerful mode you offer valuable secrets through the web site and invigorate response from people on the situation and our child is now discovering so much. Take advantage of the remaining portion of the new year. Your conducting a first class job.

    1. Thank you so means alot to me..

  9. Kayswell says:

    Its like you read my mind! You appear to know a lot about this, like you wrote the book in it or something. I think that you could do with some pics to drive the message home a little bit, but instead of that, this is excellent blog. A great read. I will definitely be back.

  10. When I initially left a comment I seem to have clicked the -Notify me when new comments are added- checkbox and now
    whenever a comment is added I receive 4 emails with the same comment.

    Perhaps there is a means you can remove me from
    that service? Many thanks!

  11. I Fashion Styles says:

    Attractive component of content. I just stumbled upon your web site and in accession capital to say that I get in fact enjoyed account your weblog posts. Any way I抣l be subscribing to your feeds or even I achievement you get entry to consistently fast.

  12. Maurine says:

    Hi there would you mind letting me know which webhost you’re utilizing?
    I’ve loaded your blog in 3 different web browsers and
    I must say this blog loads a lot quicker then most. Can you recommend a good internet hosting provider at a fair price?
    Many thanks, I appreciate it!

  13. Betsey says:

    Please let me know if you’re looking for a writer for your weblog.
    You have some really good posts and I believe I would be a
    good asset. If you ever want to take some of the load off, I’d really like to write
    some material for your blog in exchange for a link back to mine.

    Please blast me an email if interested. Thanks!

    1. Hey! what’s the name of your site?

  14. Kelsey says:

    This design is steller! You most certainly know how to keep a reader entertained.
    Between your wit and your videos, I was almost moved
    to start my own blog (well, almost…HaHa!) Wonderful
    job. I really enjoyed what you had to say, and
    more than that, how you presented it. Too cool!

  15. Malia Palazzo says:

    Right here is the right blog for anybody who would like to find out about this topic. You realize so much its almost hard to argue with you (not that I really will need to…HaHa). You certainly put a new spin on a subject that’s been written about for years. Excellent stuff, just excellent!

  16. Dexter Ferreira says:

    This is a great tip particularly to those fresh to the blogosphere. Short but very precise information… Appreciate your sharing this one. A must read article!

  17. Its like you read my mind! You appear to know a lot about this, like you wrote the book in it or something. I think that you could do with a few pics to drive the message home a bit, but instead of that, this is wonderful blog. A fantastic read. I’ll certainly be back.

  18. Filomena says:

    Thank you for the good writeup. It in fact was a amusement account it.
    Look advanced to far added agreeable from you!
    By the way, how can we communicate?

  19. Rolland says:

    I wanted to thank you for this great read!! I absolutely loved every little bit of it.
    I have got you bookmarked to look at new stuff you post…

  20. Tania says:

    Hello! This post couldn’t be written any better! Reading through this
    post reminds me of my previous room mate! He always kept chatting about this.

    I will forward this article to him. Fairly certain he will have a good read.

    Thanks for sharing!

  21. […] even as pregnancy is often a satisfying time, it may also be a source of pressure. a bran… […]

  22. Bradly says:

    Excellent post! We are linking to this particularly great post on our site.
    Keep up the great writing.

  23. Thank you ever so for you article post.Thanks Again. Really Great.

  24. Sandy says:

    Howdy! This is kind of off topic but I need some advice from an established blog.
    Is it very hard to set up your own blog? I’m not very techincal but I can figure things out pretty fast.
    I’m thinking about making my own but I’m not sure where to start.
    Do you have any points or suggestions? Appreciate it

  25. Lorenza says:

    If you want to improve your experience only keep visiting this website and be updated with the latest news update posted here.

  26. […] Director of Perinatal Services at NYC Health + Hospitals/Lincoln, tells Romper. “Fetal actions may be visible at approximately 8 weeks, and even as kicking may […]

  27. Wow, that’s what I was searching for, what a material! present here at this web site, thanks admin of this site.

Leave a Reply

Your email address will not be published.

%d bloggers like this:
Enable Notifications    OK No thanks