The part of the fetus that enters the birth canal first. When the head enters the birth canal it is called a vertex presentation. When the buttocks present first it is called a breech presentation. There are several methods used to diagnose fetal presentation: abdominal palpitation, vaginal examination, locating the fetal heart beat on the abdomen, and ultrasound scans. At or near term 96% of babies are in a vertex position, 3.5% are in a breech presentation, 0.3% in a face presentation, and 0.4% are in a shoulder presentation. About 2/3 of vertex presenting babies are in a left occiput anterior (See Anterior.) and 1/3 are in a right occiput anterior position. Up to 14% of babies are in a breech presentation until the 29th-32nd week of gestation. Many of these babies change to a vertex presentation birth. See external version.
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