[2] Head engagement is known colloquially as the baby drop, and in natural medicine as the lightening because of the release of pressure on the upper abdomen and renewed ease in breathing.

In the vertex presentation, the occiput typically is anterior and thus in an optimal position to negotiate the pelvic curve by extending the head.

[5] Factors that predispose to face presentation are prematurity, macrosomia, anencephaly and other malformations, cephalopelvic disproportion, and polyhydramnios.

[9] The piriform (pear-shaped) morphology of the uterus has been given as the major cause for the finding that most singletons favor the cephalic presentation at term.

[1] The fundus is larger and thus a fetus will adapt its position so that the bulkier and more movable podalic pole makes use of it, while the head moves to the opposite site.

On vaginal examination, the leading part of the fetus becomes identifiable after the amniotic sac has been broken and the head is descending in the pelvis.

A vertex presentation is the ideal situation for a vaginal birth, although occiput posterior positions tend to proceed more slowly, often requiring intervention in the form of forceps, vacuum extraction, or caesarean section.

[4] In a large study, a majority of brow presentations were delivered by caesarean section, however, because of 'postmaturity', factors other than labour dynamics may have played a role.