Page 188 - ترم ثاني كتاب تمريض صحة الام الكتروني

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usually experiences shorter, less intense labor. The process of labor also
depends on woman's pain threshold.

❖ Theories of Onset of Labor

1 – Prostaglandins :

* Can induce uterine contractions.

* They are formed in the decidua and membranes.

* Their level increases near term.

2 – Progesterone withdrawal:

* Progesterone supports pregnancy, it decreases the frequency of uterine
contractions . .

* A drop in progesterone level-with subsequent onset of labor could be proved only
in some animals, not in humans.

3 – Estrogen/ Progesterone:

- Estrogen helps the initiation of uterine contractions.

- Estrogen level increases near term.

4 – Estrogen-Oxytocin:

* Estrogen increases the myometrial receptors to Oxytocin “indirect effect’’.

* Oxytocin causes uterine contractions.

5 – Fetal suprarenal:

- The increase production of estrogen by the placenta near term is due to an
increase in the level its precursor: DHEAS. (dehydro- epiandrosterone sulfate)

which is produced in increased amounts by the fetal suprarenal near term with
fetal maturity.
- Anencephaly is a congenital anomaly in which the fetal vault of the skull is

absent, the brain and pituitary are atrophied. (Incompatible with life).

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