Page 44 - 33Elctronic Book (3) Normal Labor

- In These cases, the fetal suprarenal are not stimulated by ACTH and onset of

labor may therefore, be delayed.

6 – Uterine distension:

Near term, fetal growth continues and uterine growth becomes slower; the result is

increased distension of uterine muscles initiating uterine contractions. Preterm

labour may occur with early distension, e.g.: twins and polyhydramnios.

7 – Placental ischaemia:

- Resulting in lower production of oxytocin’s- an enzyme thought to be

responsible for oxytocin degradation-with subsequent rise in oxytocin level.

8 – Stretch of the lower-uterine segment:

By the presenting part near term may contribute to the onset of labor.

➢ Premonitory Symptoms and Signs of Labor:
There are symptoms and signs, which may occur in the last week or days of pregnancy
before the actual onset of labor and include:

1-Shelving:
The fundus of the uterus descends slightly &falls forwards; it brings the fetus in the
direction of the axis of the pelvis.

2- Lightening “after engagement”:
o It is the sinking of the uterus that is observed by descent of the

abdomen. This alteration is brought by engagement, which means
setting of the fetal head into the true pelvis.
o In prime gravidas, lightening usually occurs 2-3 weeks before labor.

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