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Authors: Janet Medforth,Sue Battersby,Maggie Evans,Beverley Marsh,Angela Walker

Oxford Handbook of Midwifery (51 page)

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Resting tone
: during a contraction the blood flow to the placenta
is impaired so that oxygen and carbon dioxide exchange in the
intervillous spaces is reduced. The resting tone is the relaxation period between contractions which enables placental blood flow to resume normal levels, to ensure adequate fetal oxygenation. The uterus is never completely relaxed; the measurement of the resting tone is 4–10mmHg.
Intensity of contractions
: contractions cause a rise in intrauterine pressure (amplitude), which can be recorded. Contractions rise rapidly to a peak, then slowly diminish (resting tone).
- Early labour, >20mmHg, 20–30s every 20min.
- Established labour, >60mmHg, 45–60s every 2–3min.
Formation of forewaters and hindwaters
: the result of the descent of the fetal head on to the cervix, which separates a small bag of amniotic
CHAPTER 11
Normal labour: first stage
202
fluid in front of the presenting part. The forewaters assist effacement of the cervix and early dilatation. The hindwaters fill the remainder of the uterine cavity; they help to equalize pressure in the uterus during contractions, thus providing protection to the fetus and placenta.
- Rupture of the membranes
  : is thought to occur as a result of increased production of PGE2 from the amnion during labour, together with
  the force of the contractions. In a normal labour without intervention, the membranes usually rupture between 2cm and 3cm,
  ¹around full dilatation or in the second stage.
  ²
- Show
  : displacement of the operculum as a result of effacement and dilatation of the cervix. This can occur at any time during labour, but more commonly towards the end of the first stage or at full dilatation. Sometimes a show may occur before the onset of labour, however, this is not an indication that labour is apparent.
- Fetal axis pressure
  : this is the force transmitted by the uterine contractions down the fetal spine to its head.
  Recommended reading
  Fraser DM, Cooper MA (2009).
  Myles Textbook for Midwives
  , 15th edn. Edinburgh: Churchill Livingstone.
  1. National Childbirth Trust (1989).
    Rupture of the Membranes in Labour: Women’s Views.
    London: NCT.
  2. Walsh D (2007).
    Evidence Based Care for Normal Labour and Birth. A Guide for Midwives.
  London: Routledge.
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  CHAPTER 11
  Normal labour: first stage
  204‌‌
  Diagnosis of onset of labour
  Although the three cardinal signs listed below indicate the onset of labour, each woman will be individual in her response and adaptation to labour, dependent on her parity, expectations, and pain threshold. Therefore it is recommended that individualized care is undertaken at all times. The stages of labour should be loosely adhered to, to detract from rigid routine and impersonal care.
  Pre-labour signs
- Nesting instinct and spurts of energy.
- Feeling generally unwell: flu-like symptoms or a cold.
- Diarrhoea or loose stools.
- Frequency of micturition.
- Heavy sensation/discomfort in the upper thighs and pelvic area.
- Lower backache as the fetus nestles deeply in the pelvis.
- Increase in Braxton Hicks contractions in the final few weeks.
- Feeling different, distant, and restless prior to going into labour.
- Mucoid loss or a show.
- Intermittent leakage of liquor.
- Pre-labour rupture of the membranes: most women will proceed into labour spontaneously within 24h.
  Onset of labour
- Show
  . The mucoid, blood-stained loss that is passed per the vagina known as the operculum, seals the cervical canal. Dislodgement of this mucoid plug is an early sign of uterine activity, but not necessarily an indication of the onset of labour.
- Contractions
  . The most important sign, as cervical dilatation is not possible without regular contractions of the uterus. They may commence as tightenings, but become longer, stronger, and more
  regular as labour progresses. The contractions coincide with abdominal tightenings that can be felt on abdominal palpation. The contractions may commence at 20–30min intervals, lasting for 20–30s.
- Rupture of the membranes
  . This can occur at any time during or before labour. More commonly, in a normal spontaneous labour without intervention they will rupture at a cervical dilation of 9cm or
  more. Occasionally they do not rupture until the advanced second
  stage at delivery. The amount of amniotic fluid that is lost depends on the effectiveness of the fetal presentation to aid the formation of the forewaters. With a well-fitting head, that is sufficiently engaged in the pelvis, there will be little loss of fluid, with further small leaks. If the head is poorly engaged, then the loss of fluid may well be substantial.
  Diagnosis
- Uterine activity
  : abdominal palpation, degree of discomfort or pain, observation of contractions—their regularity, strength, and length.
- History so far
  : when contractions started, evidence of a show, or ruptured membranes.
- Observation of vital signs, urinalysis, and general examination.
- Vaginal examination if clinically indicated.
  DIAGNOSIS OF ONSET OF LABOUR
  205
Observation of non-verbal behaviour, visual, and auditory signs.
All observations, clinical findings and history of the labour so far should be clearly recorded in the maternal notes.
The above information should form the basis for a plan of care to be discussed and agreed with the woman, which should be recorded in the maternity notes.
Differential diagnosis
Sometimes it may be difficult to ascertain the true onset of labour, due to compounding factors such as spurious labour and a long latent phase. The only way to manage this situation is to adopt a ‘wait and see’ policy, and it is only in retrospect that a definite diagnosis can be made.
Generally, regular contractions will cease after a few hours, with no dilatation of the cervical os, this is sometimes referred to as false labour. Obviously this can be very distressing for the woman, thinking that she has commenced labour.
In this case:
Provide extra moral support and sound explanations to ease women through this difficult time.
Some women may require pain relief.
Promote coping tactics and utilize non-pharmacological means to relieve discomfort and anxiety.
Latent phase
Defining the start of labour can be arbitrary; many women may experi- ence a long latent phase prior to the body going in to established labour. Therefore there is some debate as to how this should be managed.
Labour should be seen as a dynamic event, not a mechanical process.
Consider the individual needs and responses of the woman, as there is huge variation in experience.
Established labour may not occur until the cervix is between 3cm and 5cm dilated.
¹The latent phase is the ‘warming up’ phase prior to established labour.
Evidence suggests that labouring at home during early labour is preferable to early admission to the delivery suite.
Admission for normal labour should be at home or in assessment areas sited away from the delivery suite.
²
The environment for assessment will affect progress, depending on
certain inhibiting factors, such as medical procedures, clinical apparatus,
bright lights, language, and being observed. Women tend to be subjected to more labour intervention as a result.
³