The fetal attitude as shown in the picture above represents vertex.
The vertex is the area of the vault bounded anteriorly by the anterior fontanelle and the coronal suture, posteriorly by the posterior fontanelle and the lambdoid suture and laterally by 2 lines passing through the parietal eminences.
In the vertex presentation the occiput typically is anterior and thus in an optimal position to negotiate the pelvic curve by extending the head. In an occiput posterior position, labor becomes prolonged and more operative interventions are deemed necessary. The prevalence of the persistent occiput posterior is given as 4.7%.
The vertex presentations are further classified according to the position of the occiput, it being right, left, or transverse, and anterior or posterior:
- Left Occipito-Anterior (LOA), Left Occipito-Posterior (LOP), Left Occipito-Transverse (LOT);
- Right Occipito-Anterior (ROA), Right Occipito-Posterior (ROP), Right Occipito-Transverse (ROT);