Buccal position

…This is called vertex or occipital presentation. Inverted presentation is when the baby's chin is away from the chest, and when the top of the head, front of the head, forehead, and chin are forward, they are called vertex, frontal, brow, and face presentations, respectively. In these inverted presentations, the surface through which the baby's head passes is longer than in the vertex position, making it difficult for the baby to pass through the birth canal. …

*Some of the terminology explanations that mention "denomination" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…これを屈位，後頭位という。反屈位は児のあごが児の胸部から離れている場合で，頭頂部，前頭部，額部およびあごが先進しているのをそれぞれ頭頂位，前頭位，額位および顔位という。これら反屈位の分娩では，児頭が通過する面が屈位よりも長く，産道が通過しにくくなる。…

※「額位」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報