Labour and Delivery

Question 1

What are pro-labour factors?

Answer 1

• Oestrogen (increased levels)
• Oxytocin (increased from posterior pituitary)
• Prostaglandins (chemical transmitters)
• Endothelin
• Inflammation

Question 2

What causes the onset of labour?

Answer 2

Unknown, several theories: functional or actual decline of progesterone by the placenta at term

Question 3

What are cervical and myometrial changes mediated by?

Answer 3

Prostaglandins

Question 4

What cervical changes occur during labour?

Answer 4

Increased prostaglandin E2 and F2a in myometrium, decidual and foetal membranes –> prostagalndins promote cervical ripening and stimulate contractions (directly by acting on myometrium and indirectly by increasing oxytocin receptor expression)

Question 5

What is ‘cervical ripening’

Answer 5

Increased cervical distensability index (stretchier) through collagenolysis –> replaces collagen with amorphous substance

Question 6

What myometrial changes occur during labour?

Answer 6

Prostaglandins develop cell-cell adhesion known as gap junctions and increase levels of oxytocin receptors

Question 7

Describe the Ferguson’s reflex

Answer 7

The development of a soft cervix which then stimulate the release of oxytocin from the posterior pituitary gland –> oxytocin binding to soft cervix receptors –> contractions (start at each corner and travel caudally)

Question 8

What is Ferguson’s reflex?

Answer 8

Name given to the neuroendocrine reflex comprising the self-sustaining cycle of uterine contractions initiated by pressure at the cervix or vaginal walls

Question 9

Describe the signs of labour

Answer 9

Release of mucus plug (the show), rupture of amniotic membrane (waters breaking), painful contractions (if they come progressively closer together over a period of an hour or two and last longer than 40 seconds)

Question 10

When is labour diagnosed?

Answer 10

When regular painful uterine contractions affect progressive cervical dilation

Question 11

What are the three stages of labour?

Answer 11

Dilation of cervix from 0-10cm (uterine contractions), foetal expulsion and placental expulsion

Question 12

Describe the first stage of labour

Answer 12

Cervix dilates at rate greater than 1cm/hour and normal Braxton-Hicks contractions become painful, rhythmic contractions every 2-3 minutes –> myometrial fibres contract and retract

Question 13

Describe the second stage of labour

Answer 13

Contractions supplemented by voluntary contraction of abdominal muscles and fixing of diaphragm (increase in intra-abdominal pressure) and the foetus is delivered

Question 14

Describe the third stage of labour

Answer 14

From delivery of the baby to placental expulsion, involves uterine muscles contracting tonically (constricts blood vessels between interlacing fibres), placenta separates as the placenta bed is constricted down to half it’s size and expelled by uterine contractions

Question 15

What does normal labour depend upon?

Answer 15

The passenger, passages and powers;
Passenger - foetus helps as it has a soft skull which allows it to fit through vaginal canal
Passages - birth canal shaped to allow the passage of the baby

Question 16

What is another name for the birth canal?

Answer 16

Curve of Carus

Question 17

What is the function of the pelvic floor?

Answer 17

Support pelvic viscera, help with continence, build up effective intra-abdominal pressure (alongside diaphragm and abdominal wall muscles), helps rotate the presenting part of the foetus

Question 18

What is an episiotomy?

Answer 18

a surgical cut made at the opening of the vagina during childbirth, to aid a difficult delivery and prevent rupture of tissues.

Question 19

What is cut in an episiotomy?

Answer 19

Vaginal epithelium and perineal skin, bulbocavernosus muscle, superficial and deep perineal muscles and occasionally external anal sphincter