Labour

Question 1

What are the boundaries of the pelvic inlet?

Answer 1

anterior = superior pubic rami and upper margin of pubic symphysislateral = iliopectineal lines on each sideposterior = sacral promontory

Question 2

What occurs in cervical ripening?

Answer 2

decreased collagen productionincreased glycosaminoglycansdecreased aggregation of collagen fibresincrease in inflammatory cells, triggered by prostaglandin production

Question 3

What must changes must occur in the uterine smooth muscle to facilitate pregnancy?

Answer 3

• cell hypertrophy- increase in glycogen deposition- contractions occur to condition the muscle

Question 4

What controls uterine smooth muscle contractions?

Answer 4

• oxytocin (increases frequency of action potentials)- prostaglandins (increase in Ca2+ release from intracellular stores)

Question 5

How are contractions initiated?

Answer 5

Spontaneous depolarisation from pacemakers cells. Depolarisation spreads to each cell via specialised gap junction for coordinated contraction.

Question 6

What controls the rate of production of prostaglandins?

Answer 6

progesterone to oestrogen ratioincreased P:O ratio causes decreased prostaglandin secretiondecrease P:O ration cause increased prostaglandin synthesis

Question 7

Describe the Ferguson Reflex

Answer 7

increased stretching in the cervix and vagina causes afferent impulses to be sent to the brain and the hypothalamus stimulates massive oxytocin release from the posterior pituitary, which increases the frequency of the action potentials firing which stimulate the muscle contraction.

Question 8

What changes occur in the cervix at the start of labour?

Answer 8

• thinning and flattening of cervix- Ferguson reflex- dilation of cervix starts- amnion ruptures

Question 9

What stages must the fetus go through in order to be delivered?

Answer 9

• head flexes as it reaches the pelvic floor- head internally rotates- flexed head stretches vagina and perineum - head is delivered- head rotates and extends- shoulders rotate to follow the head- shoulders are delivered, followed by the rest of the body

Question 10

What happens in the third stage of labour?

Answer 10

uterine contractions greatly increase to shear off the placenta and position it in the upper part of the vagina/lower uterine segment. they are expelled within 10 mins

Question 11

What does the contraction of the uterus in the third stage of labour facilitate?

Answer 11

closes blood vessels and prevents significant bleeding.

Question 12

What facilitates the strong uterine contraction at the end of the third stage of labour?

Answer 12

an oxytocic drug

Question 13

Describe how the lungs are established in the newborn

Answer 13

1st breath expends the lungs and reorganises the pulmonary system. blood vessels stretch, so it is easier for them to travel through. have a dramatic decrease in pul. vascular resistance and pulmonary arterial pressure. also LA pressure rises to higher than RA pressure, which closes the foramen ovale.

Question 14

How is the foramen ovale closed?

Answer 14

reversal of blood flow when LA pressure rises to higher than RA pressure

Question 15

How is the ductus arteriosus closed?

Answer 15

SM in wall of DA is sensitive to pO2. when the massive increase occurs, this stimulates the smooth muscle to contract. the blood that enters the liver must now pass through the hepatic sinusoids.

Question 16

How is the neonate assessed once it has been born?

Answer 16

APGAR score0-10assesses colour, tone, pulse, respiration, response of neonate

Question 17

What stimulates the first breath?

Answer 17

the “trauma” of birth and the relative cold compared to mothers uterus.

Question 18

What are the characteristics of normal contractions?

Answer 18

3-4 every 10 mins lasting for 60 secs of a moderate or strong amplitude

Question 19

What must occur before dilation?

Answer 19

effaceent of the cervix– opening up

Question 20

Describe the process of labour

Answer 20

fetal membranes ruptureuterine musculature become more excitable (P:O ratio)prostaglandins are released (contraction and cervical ripening) contractions cause dilation and stimulate ferguson reflexoxytocin action, pushing fetus down into the birth canal

Question 21

What makes up the passage that the fetus must pass through?

Answer 21

pelvic inlet (10.5cm)pelvic cavity (12cm)pelvic outlet (11cm)

Question 22

What can be the cause of labour failing to progress?

Answer 22

Inadequate power- Insufficient uterine contractionInadequate passage- Abnormal bony pelvis- Rigid perineumAbnormalities of the passenger- Fetus is too big- Breech presentation

Question 23

How is the fetus monitored in labour?

Answer 23

fetal scalp electrode

Question 24

Describe a cesarean section

Answer 24

suprapubic incisiontransect and resect the linea alba and anterior layers of the rectus sheath superiorly. rectus muscles are divided laterally/though the tendinous part. allows for their reattachment

Question 25

Give some risks of C-section

Answer 25

bleeding infectiontrauma to vessel, GI tractrisk of anaesthetic

Question 26

What is operative delivery?

Answer 26

helping the fetus if it is in the incorrect position or mother is significantly tired.

Question 27

What instruments are used for operative delivery?

Answer 27

forcepsvacuum extraction

Question 28

How do progesterone levels help throughout pregnancy?

Answer 28

Prevents oxytocin from producing contractions though pregnancy, therefore helps to prevent spontaneous abortion. It also reduces prostaglandin production, therefore reducing the degree of myometrial contraction.

Question 29

What fetal landmark is used to assess the fetal head position in the birth canal?

Answer 29

fetal fontanelles

Question 30

What spinal segments are blocked in an epidural?

Answer 30

T9-S4

Question 31

Why is the patient with an epidural at risk for hypotension?

Answer 31

Lumbar sympathetic outflow blockade prevents vasoconstriction.

Question 32

Define post-partum haemmorhage

Answer 32

blood loss of greater than 500 ml after vaginal delivery (1000ml in cesarean)

Question 33

What is the most common cause of post-partum haemmorhage?

Answer 33

uterine atony- loss of muscle tone in uterus, cannot compress blood vessels

Question 34

What is another common cause of post-partum haemmorhage?

Answer 34

retained placenta

Question 35

If the uterus is firm on palpation with continuous bleeding, what other cause should you consider?

Answer 35

Laceration or trauma to the genital tract / Retained placenta

Question 36

What causes Sheehan’s syndrome?

Answer 36

Thrombosis of vessels therefore cutting of the blood supply to the anterior lobe, secondary to severe haemorrhage. This leads to necrosis of the anterior pituitary gland which increases in size during pregnancy, therefore increasing its susceptibility to necrosis.