<Li> Restitution . The fetal head turns through 45 degrees to restore its normal relationship with the shoulders, which are still at an angle . </Li> <Li> External rotation . The shoulders repeat the corkscrew movements of the head, which can be seen in the final movements of the fetal head . </Li> <P> The vagina is called a' birth canal' when the baby enters this passage . </P> <P> Station refers to the relationship of the fetal presenting part to the level of the ischial spines . When the presenting part is at the ischial spines the station is 0 (synonymous with engagement). If the presenting fetal part is above the spines, the distance is measured and described as minus stations, which range from − 1 to − 4 cm . If the presenting part is below the ischial spines, the distance is stated as plus stations (+ 1 to + 4 cm). At + 3 and + 4 the presenting part is at the perineum and can be seen . </P>

What is the medical term for birth canal
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