Labour

Definition of Labour

Labour is defined as the process by which the products of conception are expelled from the uterus after the 24th week of pregnancy.

Stages of Labour

There are three stages of Labour:

First stage

The first stage of labour is from the commencement of regular uterine contractions effecting dilatation (opening) of the cervix, culminating when the cervix is fully dilated, allowing the passage of the fetus into the birth canal. It can be further subdivided into the latent phase (early labour), where contractions are short and irregular, and the active phase (established labour), where contractions become intense and regular . Contractions (tightening) and retraction (shortening) of myometrial muscle fibres increase in length, strength and frequency as labour progresses. The mucous plug (show) is expelled as the cervix opens and the membrane sac (amnion and chorion) often spontaneously ruptures, allowing amniotic fluid to drain. Various changes can be observed in women adapting to the intensity of contractions. Expenditure of energy increases the need for hydration and food, although as labour progresses appetite is often suppressed. Women may appear hot, flushed and agitated as intense contractions may cause pain, fear and distress. Endorphin release in response to pain provides an analgesic and euphoric bolster, which may cause some women to appear calm, quiet and withdrawn. Many women find relief through their own instinctive behaviour, such as mobility, change of position and posture , warm baths or compresses, massage, relaxation and distraction techniques. As the cervix nears full dilatation further changes can be observed in the woman as she enters the ‘transition’ into second stage. The intensity of contractions increases, exacerbating pain and stress, although the contractions may be less frequent. The woman is exhausted and often expresses defeat. She may appear agitated and overwhelmed by the effort of labour, or conversely calm and removed. Increased vocalisation, spontaneous shaking, rapid movement of the legs, nausea and vomiting may be seen, and she may express an urge to bear down or push.

Second stage

The second stage of labour is the expulsive stage culminating in the birth. Commonly defined as commencing from full dilatation of the cervix which was thought to herald the urge to push, it has been suggested that second stage labour commences ‘when the presenting part has passed through the cervix and is below the ischial spines’. When the presenting part distends the genital tract and pelvic floor a surge of oxytocin is released, known as the fetal ejection or Ferguson reflex, whereby strong expulsive contractions facilitate the birth. Throughout the second stage women should be encouraged to instinctively bear down as the urge occurs with a contraction, adopting positions which increase the pelvic outlet . Prolonged breath­holding and overzealous pushing should be avoided, as this interferes with placental perfusion and may compromise the fetus. The environment should feel safe and non­threatening,with minimal intrusion from staff, and the midwife should be confident in her skill to support normal labour .

Third stage

The third stage is defined as the period from the birth of the baby to complete expulsion of placenta and membranes, and control of haemorrhage from the placental site. It can be managed physiologically or actively with the use of drugs. The placenta and membranes are examined for completeness and occasionally part, or all, of the placenta and/or membranes may be retained, requiring anaesthetic and manual removal.