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Delivery is also known as the second stage of labor, or part of the second stage of labor. It begins with complete dilatation and ends when the baby is completely out of the mother. The exact time of delivery is normally taken at the moment the baby's anterior shoulder (the shoulder delivering closest to the mother's pubic bone) is out.
As the fetal head passes through the birth canal, it normally demonstrates, in sequence, the "cardinal movements of labor." These include:
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Engagement (fetal head reaches 0 station.)
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Descent (fetal head descends past 0 station.)
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Flexion (head is flexed with the chin to its' chest.)
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Internal Rotation (head rotates from occiput transverse to occiput anterior.)
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Extension (head extends with crowning, passing through the vulva.)
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External Rotation (head returns to its' occiput transverse orientation)
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Expulsion (shoulders and torso of the baby are delivered.)
As the fetal head descends below 0 station, the mother will perceive a sensation of pressure in the rectal area, similar to the sensation of an imminent bowel movement. At this time she will feel the urge to bear down, holding her breath and performing a Valsalva, to try to expel the baby. This is called "pushing." The maternal pushing efforts assist in speeding the delivery.
For women having their first baby, the second stage will typically take an hour or two.
Delivery of the baby
During the delivery, the fetal head emerges through the vaginal opening, usually facing toward the woman's rectum.
As the fetal head delivers, support the perineum to reduce the risk of perineal laceration from uncontrolled, rapid delivery.
After the fetal head delivers, allow time for the fetal shoulders to rotate and descend through the birth canal. This pause also allows the birth canal to squeeze the fetal chest, forcing amniotic fluid out of the baby's nose and mouth.
After a reasonable pause (15-30 seconds), have the woman bear down again, delivering the shoulders and torso of the baby.
From OB-GYN 101: Introductory Obstetrics & Gynecology
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