Normal labour

Question 1

What is a ‘Normal labour’?

Answer 1

The process in which the foetus, placenta and membranes are expelled via the birth canal. It is:

• Spontaneous in nature
• Occurs during 37-42 weeks gestation
• Foetus presenting by the vertex - head down
• Results in a spontanous vaginal birth (SVD)

Question 2

It is not fully understood why labour commences, however, what are 3 key physiological changes that must occur to allow for expulsion of the foetus?

Answer 2

• Cervix softens, shortens and thins out
• Myometrial tone changes - allows for coordinated contractions
• Progesterone decreases whilst oxytocin and prostaglandins increase to allow for labour to initiate

Question 3

How many stages of labour are there?

Answer 3

3

1. First stage of labour - early/latent phase, active first stage and transition
2. Second stage of labour - passive, active
3. Third stage of labour - active or physiological

Question 4

1st stage of labour

Answer 4

The first stage of labour can be split into the latent phase/ early and the active phase. There is then a transition phase before the 2nd stage of labour.

• Latent phase / early
  
  • This can be the longest stage of labour as the body has to go through a lot of changes
  • Irregular contractions start - short-lasting, mild in tone
  • Cervical changes and dilatation up to 4cm
• Active phase
  
  • Length of active labour can vary from 8-12hrs
  • Regular, painful contractions
  • Cervix is 4-10cm
• Transition
  
  • Cervix is 8-10cm
  • May experience physical changes such as shaking, vomiting or the need to empty her bowels
  • May express that they can no longer cope

Question 5

The 2nd stage of labour

Answer 5

The 2nd stage of labour can have a passive and active element to it. This stage lasts from being fully dilated to the birth of the baby. Length of second stage varies (depends if they are non-parous or multi-parous), usually varies between 2-3 hours.

Passive

• Woman is fully dilated - assess this with vaginal examination
• No involuntary expulsive contractions

Active

• See presenting part of baby visible
• Expulsive contractions
• Maternal effort

Question 6

3rd stage of labour

Answer 6

The 3rd stage of labour is categorised from the birth of the baby to the expulsion of the placenta and membranes. Physiological and active component:

• Physiological management - up to 60 mins from birth
  
  • No use of uterotonic drugs - used to induce contraction or greater tonicity of the uterus.
  • No cord clamping
  • Placenta is delivered by maternal effort
• Active management - 30 mins from birth
  
  • Use uterotonic drugs i.e Syntocinon or Syntometrine
  • Optimal cord clamping - wait for blood to drain from the placenta before clamping and cutting the cord and then deliver it by controlled cord traction

Question 7

What is controlled cord traction?

Answer 7

Traction applied to the umbilical cord once the woman’s uterus has contracted after the birth of her baby, and her placenta is felt to have separated from the uterine wall, whilst counter-pressure is applied to her uterus beneath her pubic bone until her placenta delivers.

Basically, you carefully pull it out.

Question 8

What is meant by the mechanism of labour?

Answer 8

The mechanism of labour covers the passive movement the foetus undergoes in order to navigate through the maternal bony pelvis. Labour can be broken down into several key steps.

Question 9

What are the stages/mechanisms of labour?

Answer 9

• Engagement and descent
• Flexion
• Internal rotation
• Crowning and extension of the head or presenting part
• Restitution
• Internal rotation
• Lateral flexion of shoulders

Question 10

What mechanism does labour start with?

Answer 10

Engagemenet and descent

• This might happen before labour begins - especially in non-parous women
• In multi-parous women this may start after labour has already commenced

Question 11

How does the pressure in the uterus change in order to aid descent of the foetus into the pelvis?

Answer 11

During the first stage of labour the contraction and retraction of the uterine muscles allow less room in the uterus. Fundal dominance of the uterine contractions pushes the foetus down.

This pressure aids descent.

Once the waters have broken and if there is any maternal effort, this process may speed up.

Question 12

What is engagement?

Answer 12

This is when the largest diameter of the fetal head descends into the maternal pelvis.

Engagement is identified by abdominal palpation, where the fetal head is 3/5th palpable or less.

Question 13

What is the effect of increasing flexion throughout labour?

Answer 13

• Fundal dominance of uterine contraction exerts pressure down the fetal spine towards the occiput, forcing the occiput to come into contact with the pelvic floor.
• As the foetal head comes into contact with the pelvic floor, cervical flexion occurs.
• In this position, the foetal skull has a smaller diameter which aids navigation through the pelvis.

Question 14

When does internal rotation occur?

Answer 14

• During the contractions the leading part is pushed down towards the pelvic floor.
• As the pelvis is hammock shaped when the baby’s head pushes against it it is pushed forward. The resistance from it brings about the rotation.
• Regular contractions eventually lead to the fetal head completing the 90-degree turn.
• Baby moves from a left or right occipito transverse position to an occipital-anterior position (occiput facing forward).

This rotation will occur during established labour and it is commonly completed by the start of the second stage.

Question 15

What is crowning?

Answer 15

When the widest diameter of the foetal head successfully navigates through the narrowest part of the bony pelvis.

This is clinically evident when the head, visible at the vulva, no longer retreats between contractions.

Question 16

Extension of the presenting part

Answer 16

• The occiput slips beneath the suprapubic arch allowing the head to extend.
• The fetal head is now born and will be facing the maternal back with its occiput anterior.
• See the brow, the face and the chin be born over the pernieum

Question 17

What is Restituition?

Answer 17

• The twist of the baby’s neck that results from the internal position now being corrected. Will try to face the same direction it was facing in utero.
• Because the shoulders at the point of the head being delivered are only just reaching the pelvic floor they are often still negotiating the pelvic outlet and the fetus may naturally align its head with the shoulders.
• You may see the head externally rotate to face the right or left medial thigh of the mother.

Question 18

Lateral flexion of the shoulders is the last mechanism of labour. What happens during this stage?

Answer 18

• Aid the birth of the baby by giving gentle downward traction - assists delivery of the anterior shoulder below the suprapubic arch.
• This is followed by upward traction assisting the delivery of the posterior shoulder.
• The fetal body will be delivered by the contractions, the health professional’s role is only to assist safe negotiation of this last stage.

Question 19

Foetal lie

Answer 19

Question 20

Abnormal foetal presentations

Answer 20

Question 21

Look

Answer 21

Question 22

How do you assess foetal wellbeing during labour?

Answer 22

Foetal heart - may assess through intermittent auscultation or continuous monitoring

Question 23

What devices are used to monitor foetal heart?

Answer 23

• Pinards stethoscope - intermittent auscultation
• Hand held doppler - intermittent auscultation
• Cardiotocograph (CTG) - continuous monitoring

Question 24

What is considered a normal foetal heartrate?

Answer 24

Between 110-160 bpm

Good variability (>5bpm) and accelerations (15 bpm)

Question 25

During labour the mother is also monitored. What investigations are done to ensure the mother is coping throughout labour?

Answer 25

* BP * Pulse * Temp * Resp rate * Abdominal palpation - position of the baby, where the head is in relation to the pelvis * Vaginal examination * Monitoring of liquor (amniotic fluid)- gives an idea of how the baby is coping. * Palpation of contractions - 10 min period every half hour of 1st and 2nd stage of labour. See how strong they are and how long they are lasting. * External signs e.g Rhomboid of Michaelis and anal cleft line

Question 26

Rhomboid of Michaelis

Answer 26

Rhomboid shape at tail bone. Indicates that head is in the pelvis.

Question 27

Support through labour

Answer 27

Physical, mental and emotional support is required. * Non-pharmacological * Maternal position and mobility - if the mother can remain mobile it will reduce pain and also facilitate progress in labour * Breathing and hypnobirthing techniques - avoids pharmacological involvement * Massage and Aromatherapy * Water pools - helps in early stages of labour or even during birthing process * Pain relief * Used in low risk units * TENS machines - electrical stimulation to reduce pain * Oral analgesia i.e paracetamol and hydrocodeine * Entonox - pain relieving gas mixture * Opioids - morphine * High risk maternal unit - consultant led * Remifentanil PCA - drip * Epidural

Question 28

What is the best clinical sign to assess whether the mother is in established labour?

Answer 28

Cervical dilatation - seen by doing a vaginal examination

Question 29

A 26-year-old woman is pregnant with her first baby. She has remained very well during her pregnancy but her haemoglobin has dropped from 13g/dl at 12 weeks to 11g/dl at 28 weeks pregnant. Is this normal?

Answer 29

Yes, this is a normal physiological change in pregnancy * Haemoglobin is expected to drop during pregnancy and can drop to around 10.5g/dl * Why? During pregnancy a woman's blood volume increases by 50-70% to provide essential nutrients to the developing baby - decrease in the concentration of red blood cells in the blood

Question 30

What is induction of labour?

Answer 30

The initiation of labour using medications +/- artificial rupture of amnitoic membranes (amniotomy) +/- IV oxytocin infusion

Question 31

Indications for induction? (4)

Answer 31

* Maternal hypertension * Maternal diabetes * Pre-eclampsia * Previous still-birth or foetal death in utero

Question 32

What is done if there is failure of induction?

Answer 32

C-section

Question 33

What does the Bishop's score assess? What does a low score suggest?

Answer 33

It assesses the cervix to see whether or not it is ready for labour * A score of \<5 is an indication that the cervix is not ready for labour and requires artificial ripening - medication or balloon catheter * A score of 7 or more means that induction success is more likely and amniotomy can be done - once you do amniotomy start IV infuison of syntocinon (artificial oxytocin) to achieve adequate uterine contractions for labour/delivery * Max score = 13 Scoring is based on: * Fetal station (scored 0 – 3) * Cervical position (scored 0 – 2) * Cervical dilatation (scored 0 – 3) * Cervical effacement (scored 0 – 3) * Cervical consistency (scored 0 – 2)

Question 34

Common medications used to induce labour?

Answer 34

* Balloon catheter - first line as it is less likely to cause foetal distress than medications * Topical prostaglandin analaogues e.g misoprostol - encourage cervical dilation and thinning * IV synthetic oxytocin e.g Syntocinon - initiates uterine contractions

Question 35

Why does the use of IV oxytocin to induce labour require CTG monitoring?

Answer 35

* Risk of hypotension and hyponatraemia in the mother * Risk of foetal distress as a result

Question 36

Indications for c-section

Answer 36

* Foetal distress * Failure to progress in labour * Failed induction * Malpresentation * Severe pre-eclampsia * Placenta previa * Twins with one twin not in cephalic presentation

Question 37

C-section categories (4)

Answer 37

1 - emergency 2 - urgent 3 - scheduled 4 - elective