Mechanism of Labor
MECHANISM OF NORMAL LABOR
By: Mrs. Ashwini Khope
Lecturer, DES College of Nursing,
Shivajinagar, Pune
Mechanism of normal labor is the most important aspect to be studied in midwifery. It not only guides the actions of be performed while conducting a normal delivery but its study also ensures a safe and uneventful normal vaginal delivery. Most of us in our clinical experience must have observed how a normal delivery is conducted. But very few actually realize that in the hurry of conducting the delivery we fail to wait and observe the movements that take place during the delivery. A good midwife will always aid in conduction of a vaginal delivery and not hastily conduct it without knowing about the mechanism that is occurring inside the pelvis. Hence it is very essential to learn about mechanism of normal labor, its principles and steps to distinguish it from an abnormal one
Definition: The series of movements that occur on the head in the process of adaptation, during its journey through the pelvis, is called mechanism of labor.1
Principles
The principles are common to all mechanisms 1. Descent occurs throughout 2. The part that leads and first meets the resistance of the pelvic floor will rotate until comes under the symphysis pubis 3. The part that escapes under the symphysis pubis will pivot around the pubic bone 4. During the mechanism, the fetus turns slightly to take advantage of the widest available space in each plane of the pelvis, i.e. transverse at the brim and antero-posterior at the outlet 2
Mechanism
In normal labor, the head enters the brim more commonly through the available transverse diameter and to a lesser extent through one of the oblique diameters. Accordingly, the position is either Occipito lateral or oblique Occipito anterior. The left Occipito anterior position is commoner than the right Occipito anterior position as the left Occipito diameter is encroached by the rectum.1
The engaging antero-posterior
By: Mrs. Ashwini Khope
Lecturer, DES College of Nursing,
Shivajinagar, Pune
Mechanism of normal labor is the most important aspect to be studied in midwifery. It not only guides the actions of be performed while conducting a normal delivery but its study also ensures a safe and uneventful normal vaginal delivery. Most of us in our clinical experience must have observed how a normal delivery is conducted. But very few actually realize that in the hurry of conducting the delivery we fail to wait and observe the movements that take place during the delivery. A good midwife will always aid in conduction of a vaginal delivery and not hastily conduct it without knowing about the mechanism that is occurring inside the pelvis. Hence it is very essential to learn about mechanism of normal labor, its principles and steps to distinguish it from an abnormal one
Definition: The series of movements that occur on the head in the process of adaptation, during its journey through the pelvis, is called mechanism of labor.1
Principles
The principles are common to all mechanisms 1. Descent occurs throughout 2. The part that leads and first meets the resistance of the pelvic floor will rotate until comes under the symphysis pubis 3. The part that escapes under the symphysis pubis will pivot around the pubic bone 4. During the mechanism, the fetus turns slightly to take advantage of the widest available space in each plane of the pelvis, i.e. transverse at the brim and antero-posterior at the outlet 2
Mechanism
In normal labor, the head enters the brim more commonly through the available transverse diameter and to a lesser extent through one of the oblique diameters. Accordingly, the position is either Occipito lateral or oblique Occipito anterior. The left Occipito anterior position is commoner than the right Occipito anterior position as the left Occipito diameter is encroached by the rectum.1
The engaging antero-posterior
References: 1. D.C Dutta, Textbook of Obstetrics, 6th Edition, New Central Book Agency, Calcutta 2004, Pp: 125-129 2. Annamma Jacob, A Comprehensive Textbook of Midwifery, 2nd Edition, Jaypee brothers Medical Publishers, New Delhi, 2009, Pp :187-190 3. www.wingkingskull.com cited on 31st January 2012 4. http://pregnancy.about.com/od/laborbasics/ss/fetalpositions_2.htm cited on 27th January 2012