Mechanisms of Labour Flashcards
What is descent?
The fetus moves into the pelvis, where the sagittal suture of the fetal head enters in the transverse diameter of the pelvis.
What is flexion?
The fetus enters with an attitude of flexion, which increases when it meets the pelvic floor.
This is aided by fetal axis pressure.
The smallest diameters of the fetal head present (subocciptiobregmatic diameter)
What is internal rotation of the head?
The occiput meets the pelvic floor and rotates anteriorly.
This is supported by the forward slope of the pelvic floor.
The anterior posterior diameter of the head now fits into the anterior posterior diameter of the pelvis
What is crowning?
The occiput slides under the pubic arch to allow the widest diameter of the fetal skull through the vagina (biparietal diameter)
The head no longer retracts between contractions
What is extension?
The bregma, the forehead, the face and chin sweep the perineum and the sinciput is born
What is restitution?
The realignment of the head and shoulders
What is internal rotation of the shoulder?
The shoulder enters in the oblique or transverse diameter of the pelvis and rotates into the anterior posterior diameter of the pelvis
What is external rotation?
External rotation of the fetal head, after the shoulders enter the pelvis towards the mid-thigh of the woman
What is lateral flexion?
The baby is born following the natural curve of the pelvis towards mothers abdomen (Curve of Carus)
The anterior shoulder is typically born first
Normal labour - lie, attitude, presentation, position, denominator, presenting part.
Lie - longitudinal
Attitude - natural flexion
Presentation - cephalic
Position - left or right occipitoanterior
Denominator - occiput
Presenting part - vertex
