Page 121 - 86 human physiology part-2

Chapter 17

dilating from 4-8 centimeters. If am epidural is requested it is usually given in this phase.

• Transition In this phase the mother becomes "complete" meaning to dilation to
approximately 10 cm and full effacement. The baby begins to move through the cervix into the
birth canal.

At this point the labor enters the second stage, or the delivery of the baby. The mother begins
pushing to aid in the birth of the baby, this part of labor can last minutes, or even hours. A fetus usually
delivered head first. 'Crowning' is the term used when the fetus' head can be seen between the mothers
labia as it emerges. At this point if necessary the birth attendant may perform an episiotomy, which is a
small surgical incision in the peritoneum. This procedure is usually done to avoid severe tearing of the
mother, or to aid in the speed of the delivery.

The third stage of labor is the delivery of the afterbirth (placenta).

Oxytocin continues to be released to shrink the size of the uterus and aid in the limiting of blood
loss from the site of the placenta. As the uterus shrinks the attachment site blood vessels, some of
which can be as large as an adult finger, shrink also. The average blood loss in a routine vaginal
delivery is 400-500 cc.

There are times when a mother may need outside aid in the delivery of the baby, some of these
methods include:

• Forceps, an instrument used to cradle the fetus' head and manipulate the head under the
pubic bone to more easily pass through the birth canal.

• Vacuum Extraction, a suction cup is applied to the baby's head, and a plunger is used to
suck any air from between the suction cup and the head to create a good seal. The babies head is
then manipulated through the birth canal. This usually leaves a baby's head bruised, but the
mark fades within weeks after birth.

• Cesarean section, or C-section, is the delivery of a baby through a surgical abdominal
incision (Abdominal delivery - Abdominal birth - Cesarean section). A C-section delivery is
performed when a vaginal birth is not possible or is not safe for the mother or child. Surgery is
usually done while the woman is awake but anesthetized from the chest to the legs by epidural
or spinal anesthesia. An incision is made across the abdomen just above the pubic area. The
uterus is opened, and often brought through the incision after delivery for better visualization.
The amniotic fluid is drained, and the baby is delivered. The baby's mouth and nose are cleared
of fluids, and the umbilical cord is clamped and cut. After delivery a nursery nurse or
pediatrician check the make sure that the baby is breathing and responding. Due to a variety of
medical and social factors, C-sections have become fairly common; around 25% of births are
performed by C-section. C-sections carry some risks to mother and baby. Compared to a vaginal
birth, the risks to mother include increased risk of death, surgical injury, infection, postpartum
depression, and hemorrhage, although these are rare. Babies born by c-section are more likely to
be admitted to the ICU for breathing problems. Mothers are advised to carefully weigh the risks
of C-section versus vaginal birth.

336 | Human Physiology