Physiology of Labour

Question 1

What if the size of a non-pregnant uterus (including the width, depth and length)?

Answer 1

Around 50-70g
Width: 5cm
Length: 7.5cm
Depth: 2.5cm

Question 2

What is the size of a pregnant uterus (including the length and width)?

Answer 2

Around 800-1200g
Width: 24-26cm
Length: 30cm

Question 3

The time it takes for a primip/multip to finish the 1st stage of Labour?

Answer 3

Multip: 6-10 hours
Primip: 12-14 hours

Question 4

What is the Latent Phase?

Answer 4

This period is characterised by painful uterine contractions and variable changes of the cervix including some degree of the cervix and slow progression of dilation up to 5 cm.

Question 5

What is the Active Phase?

Answer 5

This period is characterised by regular painful uterine contractions and a substantial degree of cervical effacement until it becomes incorporated into the lower uterine segment and more rapid dilation leading from the 5cm to fully dilated- 10cm.

Question 6

What is engagement?

Answer 6

When the presenting part of the fetus descends and engages with the mother’s pelvis. Usually occurs 2-3 weeks before labour.

Question 7

What are the levels of oxytocin in pregnancy and in labour?

Answer 7

Oxytocin- synthesised in the hypothalamus and released by the posterior pituitary gland into the maternal bloodstream allowing the uterus to contract.
Oxytocin is low and stays at the same level during pregnancy and increases on the 1st stage of labour as oestrogen and prostaglandins increase uterine responsiveness to oxytocin.

Question 8

What is the different position of the fetus?

Answer 8

Vertex

• Left/Right occiput anterior (L/R OA)
• Left/Right occiput posterior (L/R OP)
• Left/ Right occiput transverse (L/R OT)
• Left/Right occiput posterior (L/R OP)

Face Presentation

• Left/Right mentum anterior (L/R MA)
• Left/Right mentum posterior (L/R MP)

Breech Presentation

• Left sacrum anterior (LSA)
• Left sacrum posterior (LSP)
• Brow Presentation
• Shoulder presentation
• the anterior position is the best position because the fetus head is tucked in and in every uterine contraction, the baby’s head hits the cervix comfortably. Also smallest diameter so will fit into maternal pelvis better
• the posterior position will not let cervix dilate evenly as some parts of the cervix will dilate more than others.

Question 9

What is the time it takes for the 2nd stage of Labour to finish for a primip/multip?

Answer 9

Primip: 60minutes
Multip: 30minutes

Question 10

What are the changes in uterine contractions and mothers secondary power during the 2nd stage of Labour?

Answer 10

Become stronger and longer but may be less frequent allowing both mother and fetus regular recovery period.
The contraction becomes expulsive and the fetus descends further into the vagina.
Mother’s response= employ secondary powers of expulsion by contracting abdominal muscles and diaphragm.

Question 11

What is Ferguson’s Reflex?

Answer 11

POSITIVE FEEDBACK
Oxytocin results in increasing contractions as the presenting part of the fetus stimulates nerve receptors in the pelvic floor.
Oxytocin also stimulates uterine prostaglandins production.
Pelvic floor will rotate the fetus normally into an anterior position.

Question 12

What is the mechanism of the 2nd stage of Labour?

Answer 12

Fetal head passes through the pelvis creating pressure on the sacral nerves and may be associated with cramps in the legs.
Fetus distends the vagina and displaces the pelvic floor.
Urethra elongates and becomes compressed → bladder is repositioned
The rectum is compressed which can cause defecation
The perineum is flattened and lengthened by the fetus
During contraction the fetal head moves forward however during intervals of the contraction, the presenting part recedes slightly.

Question 13

What is the Curvature of Carus?

Answer 13

Amniotic fluid escapes and fetus undergo a pattern of movements as it follows the shape and curve of the pelvis.

Question 14

What happens during Placental Separation?

Answer 14

The placenta separates from the wall of the uterus
and takes around 30 minutes- 1 hour.
The woman should be encouraged to sit upright and have an empty bladder as this can stop the uterus from contracting because the bladder will be full.
Skin-to-skin contact is also encouraged because oxytocin could be released.
After delivery, the uterus decreases in size which allows the detachment of the placenta.

Question 15

What are the signs of placental separation?

Answer 15

1) The uterus becomes tender and hard
2) TrickliLess common separation and starts the lower
3) Lengthening of the cord

Question 16

The Schultze Method?

Answer 16

This type of separation starts in the centre of the placenta which descends first.
The fetal surface appears at the vulva
A retroplacental clot is contained within the inverted sac- min blood loss.

Question 17

The Matthew Duncan Method?

Answer 17

Less common separation and starts the lower edge of the placenta
Placenta slips down sideways
Maternal surface appears first at the vulva
Retroplacental clot does not form
Bleeding is likely to profuse

Question 18

What are the benefits for delaying cord campling?

Answer 18

It is important that the baby is still getting nutrients and oxygen from the placenta
At least 5 minutes
Blood transfusion

Question 19

Which hormone acts on the myometrium to increase the size and number of muscle cells?

Answer 19

Oestrogen