Parturition

Question 1

What is effacement?

Answer 1

Thinning of the cervix as it stretches

Question 2

How does hCG decrease contractility?

Answer 2

inhibits formation of myometrial gap junctions

Question 3

How is oxytocin involved in labour?

Answer 3

There is a 50-fold increase in oxytocin receptor concentrations in the myometrium and endometrium before the onset of labour
Highest concentrations are found at the top of the uterus
This has a contractile effect by causing increase in MGJ

Question 4

Which hormones inhibit MGJ

Answer 4

• hCG
• progesterone
• relaxin

Question 5

Which hormones upregulate MGJ?

Answer 5

• oxytocin
• prostaglandin
• oestrogen
• melatonin

Question 6

What is the effect of CRH on uterine contractility?

Answer 6

CRH has a dual function. Promotes myometrial quiescence for most of pregnancy and then promotes myometrial contractility after the onset of parturition.

Question 7

How does CRH indirectly affect uterine contractility?

Answer 7

• stimulates prostaglandin production

- augments the myometrial contractile response to prostaglandin

Question 8

Describe how fetal HPA function contributes to the process of parturition.

Answer 8

Maternal CRH released by the hypothalamus causes increased release of fetal cortisol from fetal adrenal gland. Fetal cortisol acts on the placenta to decrease progesterone and increase oestrogen production. This results in increased output of prostaglandin from the amnion, chorion and uterus.

Question 9

Where is CRH produced?

Answer 9

Hypothalamus

Also released by the placenta

Question 10

What role does cytokines play in parturition?

Answer 10

Stimulates prostaglandin synthesis

Question 11

What is cervical ripening?

Answer 11

Cervix goes from being hard + rigid + 3cm structure to stretchy and filled with water

Question 12

What role does interleukins play in parturition?

Answer 12

Increases collagenolytic activity of cervix

Question 13

What role does NO play in parturition?

Answer 13

stimulates release of PGE2 from fetal membranes

Question 14

Where is oxytocin produced?

Answer 14

Supraoptic nucleus and paraventricular nucleus of the hypothalamus

Question 15

Where is oxytocin released?

Answer 15

Posterior pituitary

Question 16

What is the let down reflex?

Answer 16

Women who are breastfeeding release milk if they hear a baby crying

Question 17

What is the role of oxytocinase?

Answer 17

Enzyme that rapidly breaks down oxytocin, prevents receptor desensitisation

Question 18

How does oxytocin prepare the fetus for delivery?

Answer 18

Maternal oxytocin crosses the placenta and reaches the fetal brain. Causes a switch in the action of GABA neurotransmitter from excitatory to inhibitory to silence the brain and reduce its vulnerability to fetal hypoxia.
During uterine contraction, the placenta also contracts, contracting blood supply to the baby and reducing blood supply.

Question 19

Why is post-term delivery (past 42 weeks) worrying?

Answer 19

Degradation of the placenta causing fetal hypoxia

Question 20

What is primigravidae?

Answer 20

1st time having a baby

Question 21

How long should the 2nd stage of labour last for a woman having her 1st baby?

Answer 21

1-2 hours

Question 22

What is fetal axis pressure?

Answer 22

Pressure from the contractions exerts pressure down the fetal spine to its head, aiding the descent of the baby through the birth canal.

Question 23

What is valsalva manoeuvre?

Answer 23

Pushing while holding breath and chin on chest

• increases intrathoracic pressure
• reduced venous return to the heart
• reduced cardiac output
• reduced blood pressure
• reduced utero-placental blood flow