Delivery Presentations

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The delivery process

The delivery process is described in terms of fetal station, lie, attitude, and presentation.

Fetal station:
This is the relationship between the presenting part, whether that be the head, shoulder, buttocks, or feet, and two parts of the maternal pelvis called the ischial spines. Normally the ischial spines are the narrowest part of the pelvis, and are a natural measuring point for the delivery progress. If the presenting part lies above the ischial spines, the station is reported as a negative number from 0 to -3 where each number is a centimeter. If the presenting part lies below the ischial spines, the station is reported as a positive number from 0 to 3 where each number is a centimeter. The baby is said to be "engaged" in the pelvis when it reaches 0 station.

Fetal lie:
This is the relationship between the head to tailbone axis of the fetus and the head to tailbone axis of the mother. If the two are parallel, then the fetus is said to be in a longitudinal lie. If the two are at 90-degree angles to each other, the fetus is said to be in a transverse lie. Nearly all (99.5%) fetuses are in a longitudinal lie.

Fetal attitude:
The fetal attitude describes the relationship of the fetus' body parts to one another. The normal fetal attitude is commonly referred to as the fetal position: the head is tucked down to the chest, with arms and legs drawn in towards the center of the chest. Abnormal fetal attitudes may include a head that is extended back or other body parts extended or positioned behind the back. Abnormal fetal attitudes can increase the diameter of the presenting part as it passes through the pelvis, increasing the difficulty of birth.