Labour

Question 1

Initiation of labour: what does the fetus release

Answer 1

Cortisol which stimulates the placenta to increase the release of estrogen which increases oxytocin receptors in myometrium which inhibits progesterones quieting effect of myometrium (weak and irregular braxton hicks - false labour)

Question 2

At delivery : what does the fetus release

Answer 2

Oxytocin which binds to the oxytocin receptors in the myometrium. This stimulates placental release of prostaglandin.

Question 3

What will prostaglandin do

Answer 3

increases uterine contractions, pushes babies head against cervis. Cervix distorts, thins and dilates. Stimulates maternal posterior pituatiary to release oxytocin which creates a positive feedback loop releasing more prostaglandin.

Question 4

What are the 3 stages of labour

Answer 4

1) dilation stage (until cervix is 10 cm)
- fetus moves to cervical canal
- amnion ruptures releasing amnionic fluid
- pressure on cervis softens, thins and dilates
2) Explusion stage (full dilation to delivery)
- strong contractions ever 2-3 min
3) Placental stage
- uterine contraction remove placenta from endometrium
- plate sized wound but musc. contractions compress arteries to prevent hemorrhage