Labour
last written: Nov 2011, David LaPierre
last reviewed:
Introduction
Labour is a series of repetititive uterine contractions, associated with progressive cervical dilation and effacement of the cervix, and normally resulting in delivery of the fetus. We do not know the exact mechanism for onset of labour, though prostaglandins appear to be central to the process. Term labour occurs at 37-42 weeks gestation.
The goal of labour management is to support the normal process of birth and to maximize chances of vaginal birth. The goal is also to identify, potentially concerning patterns that may threaten the mother or baby and to respond as required to ensure success.
Ideally, prenatal care has been provided to identify and address risk factors, to optimize health, and to provid education. This reduces the risk of complications and allows preparation for unavoidable problems. As this can be an uncertain and fearful time, a caring attitude of the admitting health care professional is critical to prepare the patient and those accompanying her for the labour and delivery.
Contraindications to vaginal delivery, which would strongly suggest a need for Cesarean delivery, include:
- placenta previa
- vasa previa
- cord presentation
- abnormal lie or presentation
- previous classical Caesarean section or uterine rupture
- active herpes
- invasive cervical cancer
Confirming and Evaluating Labour
If in the hospital, it is important to first assess women in a triage centre, away from the central delivery suite. Active admission should be deferred until active labour is confirmed. Intervene as little as possible (ie with induction) and treat supportively, with rest and analgesia. In the meantime, it is important to inquire into and address the women's needs. Plans and strategies are important.
It can be difficult for a woman to distinguish true labour from false labour, many primiparous women visit labour triage departments for false labour. False labour is characterized by irregular and infrequent contractions that do not change in nature, are felt more in the lower abdomen and do not result in cervical change. The contractions of false labour are called “Braxton-Hicks contractions.”
It can be difficult to know when labour begins exactly. False Labour occurs with Braxton-Hicks contractions that are not associated with progressive cervical dilatation and effacement. They are usually irregular and painless, or associated with mild pain only. They can begin a number of days before true labour begins.
Labour contractions are described as more frequent and more painful. They are often associated with "bloody show", diarrhea (because of prostaglandin), or rupture of membranes. and/or their water breaking. The feeling of water breaking may vary from a slow trickle out of the vagina, to a gush of fluid followed by continuous leakage. Because amniotic fluid is continuously made, once the membranes rupture the woman should experience further leakage.
As mentioned, the history should be obtained well in advance of labour, as it changes the risk of complications and the preparations that may be required, including location of birth.
When documenting obstetrical history while the mother is in labour, use bullets and acronyms as appropriate - consise is important.
maternal age contractions
have the membranes ruptured? any complications during pregnancy
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past obstetrical history
medications
past medical history
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family history
diagnostic testing, if available
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Physical Exam
Vitals of mother and baby (fetal heart rate)
Abdominal exam to assess lie and position.
Vaginal exam to assess the cervix and presentation; a sterile glove should be used. In areas where perinatal infection rates are high, soaking the gloved hand in 0.25% chlorhexidine solution can be helpful. If in doubt regarding rupture of membranes, a sterile speculum exam can be done. With a sterile q-tip, collect some fluid that is present in the posterior vagina. A positive test for amniotic fluid occurs with nitrosine or ferning under microscope.
The Partograph
A partograph is a pictoral representation of labour. It has been in use since the 1950's, and the WHO suggests the partograph be completed for every woman in labour. Further information about implementation of the partograph is described as follows:
- Fistulacare.org - Revitalizing the partograph (a call to global action)
Duration of Labour
Duration of labour can be hard to quantify, as onset is subjective and poorly defined. Average duration and range, in hours, varies widely:
nulliparous |
multiparous |
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Stage I |
8 (2-12) |
5 (1-10) |
Stage II |
1 (0.25-4) |
0.25 (0-2) |
Stage III |
0.25 (0-1) |
0.25 (0-0.5) |
total |
9.5 (2.25-14) |
6 (1-10.25) |
First Stage - Latent Phase
What is happening?
Stage I lasts from the onset of labour to full cervical dilatation (10 cm). During the latent phase (0-4 cm) it appears little is happening, but contractions become more coordinated, stronger, and efficient. The cervix softens, effaces, begins to dilate and angle anteriorly. It lasts an average of 8 hours in nulliparous patients and 5 hours in multiparous women (ref). Contractions are relatively painless and initially occur every 3-4 minutes, but become stronger and more frequent as the cervix slowly dilates. Spontaneous rulture of membranes may occur towards the end of the latent phase.
What should you monitor?
Confirm contractions by abdominal palpation. Intermittent auscultation shold be done to identify the fetal heartbeat. A pelvic exam is necessary to assess the cervix and station.
What should you do?
During the latent phase, women will normally be encouraged to labour outside of the triage/birthing areas. It is usually safe to provide some rest and mild analgesia, ask them to labour at home or elsewhere, and to return to hospital once things speed up.
First Stage - Active Phase
What is happening?
During the active phase, which begins when cervix is 3-4 cm dilated, labour normally progresses more rapidly. The normal rate of dilatation is 0.5-1 cm/hr in nulliparious and 1.2 cm/hr in multiparous women. It lasts on average 5.8 hours in nulliparous and 2.5 hours in multiparous women (ref). Contractions can become more painful as the active phase continues, and women may feel a desire to push. However, they should wait until the cervix is fully dilated, to avoid tiring the mother.
Progress is dependent on the 3 P's:
- Power: can do amniotomy if membranes are intact or augment with oxytocin
- Passage: shape cannot be altered - gynecoid, android, anthropoid, platypoid. Android and platypoid makes passage more difficult.
- Passenger: both head diameter and position are important; flexed head is best. Position is measured by relationship of occiput to the pelvis. Head can flex and mold to the shape of the bony pelvis
Monitoring
A partogram should be started to evaluate for dystocia.
The following should be monitored during the active phase of the first stage:
- pulse, temperature, and blood pressure every 2 hours
- uterine contractions: frequency, strength, and intensity
- pelvic exam: descent, cervix every 4 hours
- fetal heart rate every 15 minutes
- ongoing analgesic needs
Comfort
Mothers may be more comfortable in a variety of poses, including sitting, standing, or showering.
Pain control, both non-pharmacologic and pharmacologic, are important to discuss and explore.
As food will not pass through the gut during labour, large meals should be avoided, especially if general anesthetics are possibly to be used. However, low-fibre, low-fat meals or drinks likely pose little hazard, and may in fact prevent complications such as ketoacidosis. (O'Sullivan et al, 2009).
Second Stage of Labour
What is happening?
The second stage of labour begins with full dilation of the cervix - to 10 cm - and ends with the birth of the baby. This is often, though not always, associated with the expulsion phase, during which the mother begins to feel the urge to bear down. The mother can signal the beginning of the second stage with facial expression, words, or other behaviours, though decreased sensation can follow epidural analgesia.
Progress is again dependent on the three P's:
- power of contractions: can be decreased by epidural analgesia
- passage
- passenger: flexion or position can be enhanced using manual, vacuum, or forceps technique
Monitoring
The following should be monitored during the active phase of the first stage:
- pulse, temperature, and blood pressure every x hours
- uterine contractions: frequency, strength, and intensity
- pelvic exam: descent, cervix every x hours
- fetal heart rate every 5 minutes while pusing
- ongoing analgesic needs
Descent of the fetal head usually only begins near full dilatation, and is measured by station, represented by the ischial spines.
Progress is defined to be slow if it is less than 1 cm/hr in nulliparous women and less than 2 cm/hr in multiparous. Arrested labour has occured if there has been no descent over one hour in nulliparous women and 30 min in multiparous women.
Pushing
Active labour starts when bearing down efforts accompany each contraction. Patients experience a strong desire to bear down, and rectal pressure typifies this. As well, nausea can occur as the cervix reaches full dilatation.
There is a variety of thoughts on effective pushing. Some advocate breath-holding, while others promote sustained release of air. Likewise, there are various thoughts on sustained pushing during contractions, vs brief (ie 5 second) pushes. Concern around sustained pushing focuses on alterations in maternal cardiac output and respiratory function, as well as reduced blood flow to the uterus due to compression of the aorta. These potentially combine to result in decreased fetal oxygenation.
It is important that the mother not become too tired; assessment of the cervix is helpful to ensure dilation is at the full 10cm before too much energy is expended. Abdominal palpation can be helpful in assessing descent, with confirmation by examination of the vulva or vagina.
Position of Mother
Hospitals frequently have women supine during delivery, though standing, kneeling, or squatting are often used in many countries. A Cochane review (Gupta, Hofmeyr, & Smyth, 2009) has found that while studies are of variable quality, upright postures appear to:
- reduce severe pain
- decrease the time of the second stage
- reduce fetal monitoring abnormalities
- decrease assisted delivery and rates of episiotomy
- increase the risk of perineal tears and postpartum hemorrhage.
Some health care providers may find the upright position more difficult, while most mothers are positive about it. Determining the proper position for a given delivery requires discussion between the mother and her team.
Preparations should be made for delivery of the infant once the second stage is reached. It is impossible to completely predict when the infant will be delivered, and it is important to be ready. Further details about delivery, including the third stage of labour (delivery of the placenta) are described under spontaneous vaginal delivery.
Resources and References
Gupta JK, Hofmeyr GJ, Smyth RMD. 2009. Position in the second stage of labour for women without epidural anaesthesia. Cochrane Review. CD002006.
O'Sullivan G et al. 2009. Effect of food intake during labour on obstetric outcome: randomised controlled trial. BMJ. 338:b784
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