The three most important planes in the female pelvis are the pelvic inlet, mid pelvis, and pelvic outlet.įour diameters can describe the pelvic inlet: anteroposterior, transverse, and two obliques. īefore discussing the mechanism of labor in the face or brow presentation, it is crucial to highlight some anatomical landmarks and their measurements. However, ultrasound does not provide much predicting value in the outcome of the labor. The ultrasound imaging can show a reduced angle between the occiput and the spine or, the chin is separated from the chest. To avoid any confusion, a bedside ultrasound scan can be performed. Brow presentation can then be further described based on the position of the anterior fontanelle as frontal anterior, posterior, or transverse.ĭiagnosing the exact presentation can be challenging, and face presentation may be misdiagnosed as frank breech. In brow presentation, anterior fontanelle and face can be palpated except for the mouth and the chin. Based on the position of the chin, face presentation can be further divided into mentum anterior, posterior, or transverse. It is possible to palpate orbital ridges, nose, malar eminences, mentum, mouth, gums, and chin in face presentation. These malpresentations are usually diagnosed during the second stage of labor when performing a digital examination. Fetal risk factors include anencephaly, multiple loops of cord around the neck, masses of the neck, macrosomia, polyhydramnios. Maternal risk factors are preterm delivery, contracted maternal pelvis, platypelloid pelvis, multiparity, previous cesarean section, black race. These risk factors may be related to either the mother or the fetus. īoth face and brow presentations occur due to extension of the fetal neck instead of flexion therefore, conditions that would lead to hyperextension or prevent flexion of the fetal neck can all contribute to face or brow presentation. Brow presentation is considered the rarest of all malpresentation with a prevalence of 1 in 500 to 1 in 4000 deliveries. In brow presentation, the neck is not extended as much as in face presentation, and the leading part is the area between the anterior fontanelle and the orbital ridges. Incidence of face presentation is rare, accounting for approximately 1 in 600 of all presentations. This typically occurs because of hyperextension of the neck and the occiput touching the fetal back. The most common presentation in term labor is the vertex, where the fetal neck is flexed to the chin, minimizing the head circumference.įace presentation – an abnormal form of cephalic presentation where the presenting part is mentum. Cephalic presentation is the most common and can be further subclassified as vertex, sinciput, brow, face, and chin. The presentation can roughly be divided into the following classifications: cephalic, breech, shoulder, and compound. The term presentation describes the leading part of the fetus or the anatomical structure closest to the maternal pelvic inlet during labor.
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