S4: Labour Flashcards
Why is labour difficult for humans?
Human women have a small amount of space in their pelvis.
What is labour?
- Labour is defined as the process of uterine contractions and cervical dilation that enables the uterus to deliver the viable foetus (>24 weeks), placenta and membranes.
- Labour is diagnosed when here are regular and increasingly painful uterine contractions (every 5 minutes) that brings about progressive cervical effacement (shortening) and or dilatation.
- Labour isn’t all about pain! It has to fit the diagnosis above where there has to be changes to cervix. Membranes does not need to rupture at this point.
What is a miscarriage?
When women delivers under 24 weeks (the foetus is not thought of as a baby before this point).
What initiates labour?
This is poorly understood. Factors include:
- Progesterone withdrawal.
- Neural stimulation from cervical pressure.
- CRH placental clock.
- Inflammatory process in cervix with prostaglandins.
What are the three stages of labour?
- First stage: This is the period of time between the onset of the regular painful uterine contractions (diagnosis of labour) to full cervical dilatation (10 cm, cervix is pushed flat against vaginal wall). This is difficult to quantify.
- Second stage: Period from full cervical dilatation to the delivery of the foetus. This is usually one hour in a nulliparous woman and half an hour in a multiparous women.
- Third stage: This is the period from the delivery of the foetus to the delivery of the placenta and membranes. This is usually less than 15 minues and if longer, active management will be needed. The women at this stage is most at risk of bleeding due to placenta.
What is the first stage of labour divided into?
- Latent Phase.
2. Active Phase.
Describe latent phase of first stage of labour
This occurs first and involves cervical changes. It is the duration for the cervix to become effaced (shortened from 3cm to less than 0.5 cm) and dilate to 3cm. Concurrent with this would be the regular uterine contractions, in a nulliparous women it could take 6-8 hours and in a multiparous women 4-6 hours. Prostaglandins are important in the initiation of labour making the cervix squishy.
Describe active phase of first stage of labour
Next is the active phase and by now the cervix is 3cm dilated. This phase is the duration for the cervix to dilate from 3 cm to 10 cm fully dilated. The rate of cervical dilatation is on the average about 1cm/hr. Oxytocin is important in strong uterine contractions.
Describe mechanism of changes to cervix during first stage of labour
Initially the cervix is closed and long, it then becomes soft as water gets drawn in.
The cervix then starts to get drawn up towards the sides of the opening to the uterus. This process can take many hours, as this continues the cervix continues to move up until there is no length (100% effacement). Now the woman enters into the active phase and the cervix starts to dilate and open up, the membranes of the amniotic sac may then start to move down and can then rupture.
What are partograms?
A partogram is a graphic representation of a woman’s labour, recorded on it is a wealth of information including:
- The rate of cervical dilatation.
- The descent of the head.
- Contraction frequency and duration, amniotic fluid consistency, colour and quantity of liquor.
- The maternal parameters of pulse, BP, temperature, urine output and its analysis.
What are alert and action lines in partograms?
Alert line is a line drawn at a rate of 1cm/hr from admission cervical dilation in active phase.
Action line is a line drawn 2-3 cn ti the right and parallel to alert line. Labour progress to the right of the action line is deemed to be slow and needing some intervention. If labour slows down then offer intervention as this is a common complaint.
What are the three main causes of a slow labour?
- Power: Commonest cause of slow labour esp. in nulliparous women, due to too weak uterine contractions or uncoordinated contractions. It is the easiest to sort out as we simply give the woman oxytocin.
- Passage: A woman with an inadequately shaped pelvis makes it more difficult for the baby to move out of the pelvic cavity. This can be a result of short stature, previous injury to the pelvis e.g. traumatic or a soft/bony tumour. Some women may have oesteomalacia or other metabolic bone diseases. Bladder is also present in the pelvis that can obstruct passage. Rectum (if constipated)can also reduce the space of the pelvic cavity and thus the passage of the baby. Fibroids could also obstruct passage of baby.
- Passenger (baby): The baby may be very large and not able to move out the pelvis. Another issue is that the baby may not be in the right position resulting it being in a sub-optimal position in the pelvis leading it to getting stuck.
Describe a women’s admission into labour
- For a woman coming into the hospital in labour, the doctor doesn’t need to be involved if things are normal.
If the pregnancy/labour is abnormal the doctor is required. - So the first thing is assessment, whether the woman is low or high risk, this will determine the team management of the woman and the appropriate care.
- A definitive diagnosis of labour is required, this may be difficult and may require a period of observation. Do not tell the women she is in labour if you are not sure.
- An agreed action plan for the woman must be adhered to and if unsure consult with the doctor or colleagues.
- There must be excellent communication between HCPs as things can go awry quickly.
What are the three basic factors that need to be provided to a women for a good labour?
- Good reassurance and one-to-one support (most important).
- Provide nutrition, hydration and pain relief.
- Allow ambulation (for women to move around).
How is a slow latent phase and active phase managed?
- An appropriate amount of foetal and maternal surveillance is required in the latent phase and allow the labour to progress naturally. Only intervene (active management) if the labour is progressing very slowly, there is an obstetric medical complication or foetal compromise is suspected. First we would artificially rupture membrane, if this didn’t work we would give oxytocin. If still not progressing may need to do caesarian.
- We generally don’t do much foetal surveillance if the pregnancy and labour are normal. Note that the foetus is hypoxic during labour while being squeezed.
- If a woman is on oxytocin we need to monitor the foetal heart as the oxytocin can result in stronger contractions and excessive contractions. Leading to the baby being hypoxic too long and acidotic and we will see this on the monitor.
