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The First Stage of Birth: Labour

During labour, the first and generally longest stage of birth at 12 to 24 hours, the contractions of the uterine muscles will cause the cervix to efface (shortening or thinning of the cervix; 0-100% thinned out) and dilate (the opening of the cervix; expressed in centimetres). Another term used to indicate progress in labour is the baby's station or the location of the baby's presenting part , in relation to certain bones in the pelvis. This indicates how much the baby has advanced or moved through the pelvis and is usually expressed in centilitres above (minus) and below (plus) the level of a certain point on the pelvis.

All these changes serve to gradually move the foetus through the cervix and vagina (or birth canal ) and out of the body.
Labour is the first stage of birth and the longest, usually being anywhere between (for a first pregnancy; in subsequent pregnancies labour is generally much shorter). Assessing the start of labour is one of the most important aspects of the management of labour.

Signs of the start of labour include:

      Painful contractions with a certain regularity
      Effacement and/or dilatation of the cervix
      Leakage of amniotic fluid
      Bloody discharge or "bloody show" (a small amount of blood mixed with mucus from the cervix) often serves as a clue that labour is about to begin.
      Rupture of the membranes or the woman's water breaking is a clear sign that something irreversible has occurred. Indeed, about 80 to 90% of women whose membranes have ruptured go into labour spontaneously within 24 hours.
     However, it should be noted that contractions may be felt long before labour actually starts, and cervical dilatation may be present weeks before the end of pregnancy.

Upon admittance to the hospital, an examination of the baby's station, presentation , position (forward/backward) and foetal heartbeat as well as the mother's weight, blood pressure, pulse, heart and breathing rates, temperature, effacement and contraction strength, duration, and frequency all are noted to see how far along labour is. Often the membranes are also checked to see if they have ruptured.

The heart rate of mother and foetus is checked about every 15 minutes as 30 to 50% of babies who develop problems or die during delivery do so without warning. Enemas and pubic shaving, were once standard procedure but, according to the World Health Organisation, have long been considered unnecessary and should not be undertaken except at the woman's request. The WHO also states that dilation of the cervix is the most accurate indication of the progress of labour. [ 2 ]

The first stage of birth is often divided into three categories: early , active , and transition . A summary of each of these stages is found in the table below:

  Length Dilation Contractions
Early Labour 2 - 9 hours 0 - 4 centimetres

30 to 60 seconds long
Start at 20 - 30 minutes apart and slow but gradually become more frequent and stronger; 5 minutes apart by the end of this phase.

Active Labour The rest of labour, usually shorter than Early phase 4 - 8 centimetres 45 to 60 seconds apart and stronger, peak sooner. Contractions become more and more intense once water breaks.
Transition Phase 10 - 90 minutes 8 -10 centimetres 60 to 90 seconds long. These contractions, which peak suddenly and peak more than once, can be as close as 1 and 1.5 to 2 minutes apart. May feel as if the contractions are right on top of each other.
Source: [ 1 ]

The transition phase is the sign that labour is almost over and the woman and baby are moving into the second stage of birth: delivery .

The information in this page is presented in summarised form and has been taken from the following source(s):
1. Bayfront's Health Adventure, A Woman's Way to Health: http://www.bayfront.org/
2. Care in Normal Birth: A Practical Guide. Report of a Technical Working Group, World Health Organisation, Department of Reproductive Health and Research, 1999. http://www.who.org


Other HON resources 
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Contractions
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Labor Onset
Labor Stage, First
Uterine Contraction

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Labor Onset
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  http://www.hon.ch/Dossier/MotherChild/birth/labour.html Last modified: Oct 20 2004