MECHANISM OF LABOUR/RIGHT OCCIPITO POSTERIOR/DHANYA DEEPU/OBG

Lie – Longitudinal Presentation – Cephalic Presenting part – Vertex Attitude – Deflexion Denominator – Occiput Position – Right / Left Occipito-posterior Mechanism of Labour- In favourable circumstances (90%)– Engagement – Deflexion causes delayed engagement. The head engages through the right oblique diameter in ROP and left oblique diameter in LOP. The engaging diameter of the fetal head is biparietal (9.5 cm) and the suboccipitofrontal (10 cm) or occipito-frontal (11.5 cm) and reaches the pelvic floor. Descent -It is a continuous process. Flexion – Good uterine contractions result in good flexion of the head. Internal rotation of the head – occiput is the leading part, it rotates 3/8 th of a circle (135) anteriorly to lie behind the symphysis pubis. As the neck cannot sustain such amount of torsion, the shoulders rotate about 2/8th of a circle and occupy the right oblique diameter in ROP and the left oblique in LOP with 1/8th of a circle torsion of the neck still left behind. Crowning – Further descent occurs the occiput slips beneath the subpubic arch, the biparietal diameter stretches the vulval outlet without a recession of the head. Extension of the head – After crowning the driving force pushes the head in the downward direction and the parts of the head are born by stretched vulval outlet, these are vertex, brow & face, as the chin sweeps the perineum it comes closer to maternal anal opening and drops the head. Restitution – There is the movement of restitution to the extent of 1/8th of a circle in the opposite direction of internal rotation of the head. External rotation of the head with internal rotation of shoulder – The external rotation of the head occurs through 1/8th of a circle in the same direction of restitution as the shoulders rotate from the oblique to anteroposterior diameter of the pelvis and come behind the symphysis pubis. Birth of shoulder & trunk by lateral flexion – As the shoulder is positioned in the anteroposterior diameter of outlet further descent occurs, the anterior shoulder escape the subpubic arch and the posterior shoulder passes over the perineum, then rest of the body is born by the lateral flexion. In unfavourable circumstances / Malrotation / Non-rotation (10%) – occipitoposteriorposition #leftoccipitoposterior #rightoccipitoposterior #longrotation #shortrotation #deeptransverswarrest #obliquetransversearrest