The three stages of labour, induction methods and drugs for pain relief
60-second summary
This CPD article will help if you ever need to discuss childbirth with a mother-to-be, and explains what might happen if labour does not go according to plan.
What are the three phases in the first stage of labour?
The first or latent phase is when contractions are mild and irregular and the cervix softens. In the active phase, contractions get stronger, while in the final transition phase contractions become intense and the cervix is fully dilated.
What happens in the second and third stages of labour?
The baby's head appears in the second stage and, with a few more contractions, the rest of the body. The third stage involves the delivery of the placenta and membranes.
Spontaneous labour usually occurs after about 40 weeks of pregnancy and is divided into three stages.
The first stage
Signs that labour may start soon include engagement of the baby's head, strong Braxton Hicks contractions and loss of the mucous plug that has been blocking the cervix - this is known as the show. In 15 per cent of pregnancies the waters break, either suddenly or gradually, before contractions start. A woman is classed as being in true labour once her cervix has dilated beyond 2-3cm and she is experiencing regular contractions.
The first stage of labour is itself divided into three phases. The first is the latent phase when uterine activity begins; contractions are usually mild and irregular, and the cervix thins and softens (effacement). This phase can last for many hours, especially in first-time mothers. Pain may present in the lower back and there is often the need to empty the bowels.
The active phase is said to have started once the cervix is at around 3cm and regular, stronger contractions are established. The nature of the contractions changes and the pain shifts from just the lower part to the whole of the uterus. Contractions become more regular until they occur every two minutes, with each one lasting around 60-90 seconds.
The duration of this stage varies according to whether a woman has had a baby before. In first-time mothers the cervix dilates an average of 1cm each hour, but it is much faster in subsequent labours. If the waters have not broken spontaneously and the cervix has reached about 5cm they may be broken artificially to release prostaglandins which, together with the increased pressure of the baby's head against the cervix following removal of the amniotic fluid, causes contractions to speed up.
The final phase of the first stage of labour is known as transition and begins when the cervix reaches 10cm and is fully dilated. This phase may only last minutes or can go on for more than an hour. Contractions are very intense and long, and the woman often feels a strong urge to push. This is a sign she is entering the second stage of labour.
The second stage
Once the cervix is fully dilated the mother, with advice from the midwife, pushes the baby's head downwards into the pelvis with each contraction. Gradually the baby's head appears (this is called crowning) and at this point it usually only takes a few more contractions for the head, shoulders then the rest of the body to be delivered. For first labours this stage lasts an hour on average but in subsequent labours it lasts just minutes.
Throughout the second stage the baby's heart is monitored after each contraction or push. The contractions are also monitored, as they sometimes fade away - in which case a low-dose syntocinon (a synthetic equivalent of oxytocin) infusion is used to restore strong, regular contractions.
If the second stage takes too long an episiotomy (a cut through the perineum) or the use of forceps or vacuum extraction (ventouse) may be recommended.
The third stage
The final stage of labour involves the delivery of the placenta and membranes. Once the umbilical cord has been cut, the placenta must be delivered promptly. This stage is usually managed with an injection of Syntometrine, a combination of syntocinon and ergometrine. It is injected into the woman's thigh muscle as soon as the baby's head and first shoulder are delivered. It works by initiating a strong sustained contraction so that the placenta separates from the uterus and begins to be expelled. The midwife carefully pulls the umbilical cord until the placenta and membranes are delivered.
Without the injection, delivery of the placenta still occurs naturally but takes longer and is associated with increased risk of haemorrhage.
Induction
If a pregnancy goes beyond 40 weeks it is overdue. At 41 weeks an examination of the cervix may be offered and a membrane sweep performed. This involves the midwife sweeping a finger around the cervix in order to release prostaglandins and hopefully kick-start labour.
Induction is recommended if labour has not started by 42 weeks. Beyond this point the risk of foetal distress and stillbirth increases because of decreased functioning of the placenta and increased size of the baby.
Induction is also indicated if the baby is distressed, if there are maternal complications, or if the waters break but contractions do not start within 24 hours. Induction is only used when necessary as it is unpredictable and there is less chance of a normal vaginal delivery.
As long as the baby is head-down and engaged or nearly engaged, a prostaglandin pessary or gel is inserted into the vagina to ripen the cervix if necessary. This is repeated after six hours and subsequently if needed. The baby is monitored for 30 minutes after each dose. Artificial rupture of membranes (ARM) may be offered once the cervix is 2-3cm dilated. This releases prostaglandins, which aid contractions and may be enough to get labour started. If not, a syntocinon drip is started to stimulate the uterine muscles to contract. An initial low dose is gradually increased until contractions are established at around three every 10 minutes.
This rapid start of contractions means that continuous monitoring of the baby and mother are required and often an epidural is recommended.
Caesarean section
At least one in five babies in Britain are born via caesarean section, either electively or as an emergency. Most elective caesareans are performed because vaginal delivery is considered risky for the mother or baby, and the reasons include breech presentation (the baby is bottom-down), placenta praevia (when the placenta covers the cervix), multiple pregnancy, maternal illness and pre-eclampsia.
Emergency caesareans may be performed when the progression of labour is considered to be too slow or when there is foetal distress. Caesareans are usually performed under epidural or spinal block, but general anaesthetic may be needed.
Pain relief
Pharmacological
During the very early stages of labour, paracetamol may be used to ease the pain of contractions. The next step is Entonox, which is a 50:50 mix of nitrous oxide and oxygen (referred to as gas and air). It does not give complete pain relief but makes the contractions more bearable, is quick to work and wears off quickly after use, and can be used in home births. It does not sedate the mother but may make her feel light-headed and nauseous.
The woman is in full control and should be advised to start taking deep slow breaths when she feels the contraction beginning. There are no harmful side effects to the baby.
Most women find gas and air beneficial during the early stages of labour but, as it progresses and contractions become stronger, extra pain relief may be desired.
Opioids are the next step in managing pain. While any opioid can be used, pethidine is the most common as it can be prescribed and administered by midwives. An intramuscular injection of pethidine works within 15-20 minutes and lasts for around three to four hours.
There are a number of disadvantages to using opioids during childbirth because, as well as causing sedation, nausea and vomiting in the mother, they cross the placenta causing drowsiness in the baby leading to problems in establishing breastfeeding. If given too close to birth the baby may suffer sedation and breathing difficulties for which an injection of naloxone is indicated.
For complete pain relief an epidural is used. It has to be administered by an anaesthetist. A traditional epidural involves an injection of local anaesthetic (sometimes in combination with an opiate) through a catheter into the epidural space in the spine.
The mother's blood pressure is checked regularly after an epidural, as hypotension is a common side effect caused by the anaesthetic blocking the nerves that control blood vessels in the legs and pelvis. An intravenous drip is always inserted before an epidural, to allow administer fluids to be given if necessary. A catheter is also often inserted because the nerves that control the bladder are also blocked.
Full anaesthesia should be achieved after 20-30 minutes and may be topped up when required, usually every three to four hours. Some hospitals offer mobile epidurals where a lower dose of anaesthetic is used. These leave the legs unaffected so that the woman can remain mobile and without need of catheterisation.
An epidural should not cause drowsiness or nausea in the mother and the anaesthetic does not cross into the placenta. However, contractions cannot be felt, which makes pushing at the right time and in the correct way difficult. As the final stage is approached, the dose of anaesthetic may be reduced to avoid this problem and reduce the risk of intervention.
Some women develop a headache, backache, tingling or numbness in their legs after the epidural. These ease over time, although some believe epidurals can cause long-term back pain.
Non-pharmacological
Most women are able to ease the pain of early, mild contractions using deep breathing techniques and by staying mobile.
Probably the most popular of the drug-free methods of pain relief is a TENS machine (transcutaneous electrical nerve transmission), which conducts a small electric current through the skin to stimulate production of endorphins, which block nerve transmission to the brain. Specific maternity TENS machines are provided by some hospitals or are available for rental from pharmacies. They are easy to use, the woman is in complete control and able to remain mobile, and there is no effect on the baby. They cannot be used in water, however.
Hydrotherapy in a bath or a birthing pool is increasingly recognised as a good way to ease the pain of contractions. The warmth of the water aids relaxation and the buoyancy gives support and relieves the pressure of the babyÕs head in the pelvis. Extended periods in water are usually not recommended once the waters have broken and in most cases the baby will be delivered out of water unless the midwife is experienced enough to deliver the baby under water.
Reflect
What is syntocinon and when is it administered? When might induction of labour be recommended? What are the advantages and disadvantages of using pethidine in labour? How does a TENS machine work?
Plan
This article describes the three stages of labour and includes information about induction, caesarean section and the use of drugs to aid labour. It also discusses pharmacological and non-pharmacological pain relief such as pethidine, Entonox and TENS.
Act
Evaluate
Are you now familiar with what happens during the three stages of labour? Do you know what drugs might be used? Are you confident in your ability to discuss pain relief in labour with a patient?
References
1. Regan, L (2005). Your pregnancy week by week. London: Dorling Kindersley.
2. NHS Choices (2010) www.nhs.uk/planners/pregnancycareplanner
3. Mumsnet (self-help group) (2010) www.mumsnet.com
4. National Childbirth Trust (2010) www.nctpregnancyandbabycare.com
Get a CPD log sheet for your portfolio when you successfully complete the 5 Minute Test online.
Registering for Update 2010 costs £37.60 (inc VAT)
