1. Parturition & Postnatal Development
Chapter 23

2. Parturition & Postnatal Development
Pregnancy terminates with the birth process or parturition
For some time prior to this event, secretion of estrogen at increasing levels has induced minor contractions of the uterine wall—Braxton-Hicks contractions

3. Factors Contributing to the Labor Process
as birth approaches, progesterone levels decrease
prostaglandins synthesized which may initiate labor
stretching uterine tissue stimulates release of oxytocin
oxytocin stimulates uterine contractions
fetal head stretches uterus
positive feedback results in stronger and stronger contractions and greater release of oxytocin

4. Birth Process
A positive feedback mechanism propels the birth process

5. Stages in Birth Stage 1— dilation stage Stage 2—expulsion stage
Stage 3—placental stage

6. Stages in Birth
The head of the fetus begins to be pushed into the cervical canal causing dilation until the cervix is expanded to a diameter of about 10 cm
This period of labor is considered the first stage of labor
May last up to 24 hours or more
Second stage of labor continues from the maximum cervical dilation to the exit of the fetus
Abdominal muscle contractions are stimulated by positive feedback
May last from 1 minute up to 1 hour

7. Stages in Birth
After birth, the placenta separates from the uterine wall and is pushed through the birth canal by another wave of contractionsthird stage of labor
Usually accompanied by bleeding
Blood loss is usually restricted as contractions continue and compress broken blood vessels
After parturition, levels of estrogen and progesterone in the blood fall dramaticallydue to the loss of the source the placenta
Levels are restored once the menstrual cycle is resumed by the release of GnRH by the hypothalamus
Menstrual flow usually returns about 8 to 12 weeks after parturition

8. Lactation Lactation is the production of milk by the mammary glands
placental estrogens and progesterone stimulate further breast development
estrogens cause ductile system to grow
progesterone causes alveolar glands to develop
placental lactogen also produces changes in breast
prolactin is released about the 5th week of pregnancy
breast production does not begin until after birth

9. Ejection of Milk
forcing milk to be ejected—referred to as milk letdown

10. Ejection of Milk
Myoepithelial cells contract to eject milk from an alveolar gland

11. Milk Composition
First several days of milk production results in colostrum which contains small amounts of fat and lactose and is though to contain antibodies to protect the nursing child from infections
After several days of production, the milk increases in fat and lactose, while the antibodies decline

12. Continuing Lactation
If nursing continues, prolactin and oxytocin continue to cause the production of milk
Once nursing has stopped for several days, the ability of the mammary glands to respond to prolactin is lost milk production will stop until the next pregnancy

13. Postnatal Period Neonatal period birth to end of 4th week
newborn begins to carry on respiration, obtain nutrients, digest nutrients, excrete wastes, regulate body temperature, and make cardiovascular adjustments
Infancy
end of 4th week to one year
growth rate is high
teeth begin to erupt
muscular and nervous systems mature
communication begins

14. Postnatal Period Childhood Adolescence one year to puberty
growth rate is high
permanent teeth appear
muscular control is achieved
bladder and bowel controls are established
intellectual abilities mature
Adolescence
puberty to adulthood
person becomes reproductively functional and emotionally more mature
growth spurts occur
motor skills continue to develop
intellectual abilities continue to mature

15. Postnatal Period Adulthood adolescence to old age
person remains relatively unchanged anatomically and physiologically
degenerative changes begin
Senescence
old age to death
degenerative changes continue
body becomes less able to cope with demands placed on it
death results from various conditions and diseases