Labour

last written: Nov 2011, David LaPierre, Kim Colangelo
last reviewed: Dec 2015, Isabelle Milot

 

 

Introduction

 

Labour is a series of repetitive 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 a healthy outcome.

 

Ideally, prenatal care has been provided to identify and address risk factors, to optimize health, and to provide 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 include:

 

 

 

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 in latent labour and treat supportively, with rest and analgesia.

 

 

  • history
  • physical exam

History

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. Braxton-Hicks begin at the end of pregnancy and can lead one to confuse the latent phase of first stage with false labour.

 

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. 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 - concise is important.

maternal age

gestational age

contractions

  • when did they start?
  • how frequent are they coming?
  • how long do they last?
  • are they getting worse?
  • have they tried anything for pain?
  • abdomen soft after contractions?

have the membranes ruptured?

any complications during pregnancy

  • vaginal bleeding, membrane rupture
  • infections, rash fever
  • exposures (smoking, EtOH, drugs, rads)
  • high blood pressure
  • gestational diabetes
  • admissions to hospital

past obstetrical history

  • all pregnancies and details
  • year, hospital
  • gestational age at delivery
  • antenatal complications
  • mode of delivery
  • labour and delivery complications
  • gender
  • weight
  • postpartum complications

 

medications

  • including preconceptual

past medical history

 

 

family history

  • obstetrical complications
  • diabetes
  • hypertension
  • DVT
  • congenital abnormalities (give examples)
  • inherited diseases (ethnicity)

diagnostic testing, if available

  • group B strep status
  • screening bloodwork
  • antenatal screening, ie ultrasounds

 

During the initial assessment, inquire into and address the women's needs, plans and strategies for labour.

Physical Exam

Begin by assessing maternal and fetal vitals.

Perform an abdominal exam to assess lie and position, as well as contractions.

Perform a 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.

 

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First Stage

The first stage of labour lasts from onset of labour to full cervical dilation (10cm). This stage is divided into two phases - latent and active - and the management of each phase is very different.

 

Latent First Stage

Onset of latent first stage begins when the mother detects contractions, although these are often uncoordinated and range from mild to moderate in strength, usually more than 5 minutes apart. These contractions result in the cervix softening, effacing, beginning to dilate and angling anteriorly. Latent labour is often dilation from 0-4cm, but this can be different in each woman. Since active first stage is characterized by regular contractions that cause cervical change, the transition from latent to active can be subtle and drawn out. Since most women spend this phase at home, there is little research about the average duration. Women are often encouraged to ignore these early contractions, take a bath and over-the-counter analgesia, and rest. A woman in latent labour SHOULD NOT be admitted to a labour and delivery suite due to risk of unnecessary intervention.

 

Oxytocin is released in response to cervical stretch during labor. Oxytocin release causes uterine contractions, which pushes against the cervix, which in turn causes more oxytocin release. This positive feedback loop (the ferguson reflex) happens quickly because of oxytocin's cell surface signaling. Uterine contraction also causes prostaglandin release, another positive feedback loop. Once the baby is born, the sound of the baby's cry, and the suckling reflex act on higher brain centres to induce oxytocin release and remove inhibition on prolactin release, causing both smooth muscle contraction and milk secretion.

 

What should you monitor?

The woman should remain at home for the duration of latent labour unless there are risk factors, such as rupture of membranes, decreased fetal movement, vaginal bleeding (other than mucous/show), etc. There is insufficient evidence or recommendations on fetal surveillance for this phase as women are discouraged from being admitted to the laboring unit at this point.

 

If a woman presents to labour and delivery in latent labour, the care provider should assess maternal vitals, fetal position, fetal heartbeat via intermittent auscultation, and perform a vaginal exam to assess progress. The woman’s psyche should also be assessed: is she exhausted? Panicked? Overwhelmed?

 

If the woman is deemed to be in latent labour, she can be offered analgesia and comfort measures, and be sent home to await active labour.  The care provider should take special care to reassure and educate her about the normal progress of labour, and recommend rest and relaxation at home.

 

 

Active First Stage

As stated above, active labour is defined as progressive cervical change caused by regular contractions. This often begins at 3-4 centimeters dilation, but might not be until 5 cms for many primips (ACOG). Different organizations define and manage active labour differently. For example, ACOG states labour dystocia should not be diagnosed before 6cm, as many times, women just need more time to labour and/or analgesia. The important thing to keep in mind is safety and progress. Even if dilation is slower than expected, if the mother and baby are safe and vitals remain normal, more time is reasonable.

 

For many years, the Friedman curve was used to determine normal progress in active labour, but recent research recommends care providers move away from viewing labour through this strict, unforgiving lens, as for most women, labour progress is not linear.

 

Historically, the normal rate of dilation for a nullip was 0.5-1cm/hr and 1.2cm/hr in multiparous women, lasting on average 5.8 hours for nullips and 2.5 hours in multips. According to research referenced in a 2014 ACOG statement, the rate of active phase dilation varies from 0.5 cm/h to 0.7 cm/h for nullips and 0.5 cm/h to 1.3 cm/h for multips, and these ranges reflect the fact that as the women dilates more, labor progresses more quickly.

 

As labor progresses towards full dilation, a natural urge to push usually starts as the cervix melts away and the fetus descends into the vagina. In some cases, the urge to push can be felt earlier than full dilation, as seen in many OP babies, as the occiput puts more pressure on the rectum. The woman should be encouraged to breathe until there is no more cervix felt, and often anti-gravity positions such as hands and knees or left lateral can help alleviate or reduce this premature urge to push.

 

Progress is dependent on the four P’s (MoreOB):

Powers: effectiveness of contractions or bearing down efforts; can do amniotomy if membranes are intact or augment with oxytocin

Passenger: fetal position, attitude, size and presence of anomalies. Both head diameter and position are important; a flexed head is best so it can mold to the shape of the bony pelvis. Position of the fetus is measured by the relationship of the occiput to the pelvis.

Passage: shape cannot be altered - gynecoid, android, anthropoid, platypelloid. Android and platypelloid makes passage more difficult. Also pertains to soft tissues (tight perineum, full and distended bladder, tumours etc.)

 

Psyche: woman’s expectation and anxiety levels, fears, emotions

 

Monitoring

A partograph is a pictoral representation of labour and should be started during the first stage to evaluate for dystocia. 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 at Fistulacare.org - Revitalizing the partograph (a call to global action).


The following should be monitored during the active phase of the first stage:

The cervix should be assessed:

 

Comfort

Mothers may be more comfortable in a variety of poses, including sitting, standing, or showering.

Pain control, both nonpharmacologic 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

The second stage of labour begins with full dilation of the cervix (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 four P's as mentioned above.

This stage is also divided into two phases - the latent and active - and the management of each phase is very different.

 

Latent Second Stage

A woman and her fetus are to be monitored just as they were in the first stage of labour. Some women, especially while on epidural analgesia, will sit at full dilation for 1-2 hours without feeling an urge to push, which allows for passive descent of the fetus. The duration of latent second stage should not be included in what is considered normal duration of second stage, as this is referring to active pushing. Nausea can occur as the cervix reaches full dilatation.


Active Second Stage

In the active second stage, a woman is pushing with her contractions to expel the baby, whether due to the fetal ejection reflex that causes a woman to bear down spontaneously (felt like rectal pressure), or with active coaching which is often needed during epidural analgesia.  


Monitoring

The following should be monitored during active second stage:

 

Descent of the fetal head usually only begins near full dilatation, and is measured by station, represented by the ischial spines.

Dystocia of second stage should not be diagnosed before there has been:  

These longer durations allow for the effects of epidural analgesia or fetal malposition, and as long as progress is being made and mother and fetus are doing well, the care provider may wish to continue pushing.

 

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:

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.

 

 

 

Third Stage of Labour

The third stage of labour begins with delivery of the fetus and ends with delivery of the placenta. Management of this stage under non-operative conditions is detailed in spontaneous vaginal delivery.

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Resources and References

 

ACOG Obstetric Care Consensus: Safe Prevention of the Primary Cesarean Delivery, Number 1, March 2014.

 

MoreOB, Management of Labour. 14th Edition, 23 September 2015.

 

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

How to tell when labour begins. The American Congress of Obstetricians and Gynecologists. Feb 2009.

 

Pelvic Exam During Labour – Brookside Press