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:
-
Engagement (fetal head reaches 0
station.)
-
Descent (fetal head descends past 0
station.)
-
Flexion (head is flexed with the
chin to its' chest.)
-
Internal Rotation (head rotates
from occiput transverse to occiput anterior.)
-
Extension (head extends with
crowning, passing through the vulva.)
-
External Rotation (head returns to
its' occiput transverse orientation)
-
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
