Labour is the term used to describe the process of childbirth, where, after approximately 28 weeks of pregnancy, the baby, placenta, and fetal membranes are expelled from the uterus through the birth passage.

Alternatively, labour can be defined as the series of rhythmic contractions and relaxations of the uterine muscles that lead to cervical effacement (thinning of the cervix) and cervical dilatation (opening of the cervix), ultimately resulting in the delivery of the products of conception.

Normal Labour

Labour is considered to be normal when it meets these criteria:

• Occurs at term gestation (around the expected due date).

• Begins spontaneously without medical induction.

• The baby presents in the vertex position (head first).

• Progresses and completes within a timeframe of approximately 12 to 18 hours.

• Proceeds without the development of complications.

• Results in no injury to either the mother or the baby.

• Occurs without any external assistance or interventions.

THREE P’S OF NORMAL LABOUR

These are the critical factors influencing the progress of normal labour:

• Powers: Refers to the uterine contractions, their strength and effectiveness in dilating the cervix and pushing the baby down.

• Passage: Represents the maternal pelvis, considering both its bony structure, size, and shape, and the soft tissues of the birth canal.

• Passenger: Encompasses the fetus itself, including its size, position, and presentation (part of the fetus leading the way through the birth canal), as well as the amniotic sac (bag of forewaters).

Types of Labour

1. True Labour: Characterized by consistent and regular uterine contractions that, initially mild, gradually become more intense and frequent. Crucially, these contractions cause progressive cervical dilation.

2. False Labour: In contrast, false labour involves irregular uterine contractions that do not lead to cervical change. These contractions can be painful and may feel strong, particularly when resting, but often lessen or disappear with activity and movement.

   • No Cervical Dilatation: The cervix remains closed and does not open.

   • No Show: Absence of the mucus and blood discharge associated with true labour.

   • Pain Location: Pain is typically felt in the lower abdomen and tends to stay in one area, rather than radiating.

   • Pain Pattern: The pain is often continuous and lacks a clear, rhythmic pattern.

   • Pain Relief: Discomfort may lessen after an enema.

   • Abdominal Hardening: The abdomen may not noticeably harden with each contraction as in true labour.

Signs of Impending Labour

These are changes that typically occur in the final weeks of pregnancy, often termed the pre-labour period, indicating that labour is approaching.

1. Lightening:

   • Approximately 2 to 3 weeks before labour starts, the lower segment of the uterus expands. This allows the baby’s head to descend lower into the pelvis, a process known as engagement.

   • Simultaneously, the symphysis pubis joint widens, and the muscles of the pelvic floor become more relaxed and softened, further facilitating the descent of the uterus and baby into the pelvic cavity.

2. Cervical Changes:

   • In the days and weeks leading up to labour, the cervix undergoes “ripening”.

   • It becomes softer in consistency, likened to the softness of the lower lip.

   • There may be some degree of cervical effacement (thinning) and slight cervical dilatation (opening) even before labour officially begins.

3. False Labour:

   • False labour involves painful uterine contractions that, despite the discomfort, do not cause any progressive changes to the cervix.

   • These contractions are often an intensified form of Braxton Hicks contractions, which are painless uterine tightenings experienced throughout pregnancy, starting as early as 6 weeks gestation.

   • False labour contractions can occur intermittently for days or even for 3 to 4 weeks before the onset of true labour.

4. Premature Rupture of Membranes (PROM):

   • Normally, the amniotic membranes rupture (water breaks) towards the end of the first stage of labour.

   • When membrane rupture occurs before the onset of labour contractions, it is termed Premature Rupture of Membranes (PROM).

   • PROM occurs in approximately 12% of pregnancies.

   • In about 90% of women with PROM, labour will begin spontaneously within 24 hours.

5. Bloody Show:

   • During early pregnancy, a mucus plug forms in the cervical canal due to secretions from cervical glands. This plug acts as a protective barrier, sealing the cervix throughout pregnancy.

   • Bloody show is the expulsion of this mucus plug. It occurs as the cervix begins to soften, efface, and dilate, often causing the plug to be dislodged, sometimes mixed with a small amount of blood from the dilating cervix.

6. Energy Spurt:

   • Many women experience a sudden surge of energy approximately 24 to 48 hours before labour begins.

   • After feeling fatigued for weeks, they may unexpectedly find themselves feeling energetic and motivated.

7. Gastrointestinal (G.I.T) Upset:

   • Some women experience diarrhea, nausea, vomiting, or indigestion in the days leading up to labour, when there is no other obvious cause, such as food poisoning or illness.

   • It is suggested these gastrointestinal changes might be an early indicator of impending labour, although the exact reason for this is not fully understood.

Signs of Labour

Labour signs can be classified into two categories:

1. Premonitory Signs (Signs suggesting labour is approaching)

2. Actual Signs (Definitive signs that labour has begun)

Premonitory Signs

• Lightening: Occurs 2-3 weeks before labour onset. The baby descends further into the pelvis (engages). This reduces pressure on the diaphragm, making breathing easier for the mother and providing a feeling of relief.

• Frequency of Micturition: Increased urinary frequency occurs due to pelvic congestion and the descending baby’s head putting pressure on the bladder, reducing its functional capacity.

• Effacement of the Cervix: Cervical effacement is the process where the cervix softens, thins, and shortens. The cervix is drawn upwards and gradually integrates into the lower uterine segment.

• Braxton Hicks Contractions: These contractions become more pronounced and noticeable, sometimes causing anxiety. The mother may experience backache or pains while walking due to the relaxation of pelvic joints in preparation for birth. This can lead to the mother believing she is in true labour.

Actual Signs

• Regular Uterine Contractions: The key sign of true labour is regular, painful, and rhythmic uterine contractions. Initially, they may be mild, but they progressively increase in intensity, duration, and frequency.

• Dilatation of the Cervix: This is the opening of the cervical os (the opening of the cervix) from a closed state to a diameter large enough to allow the baby to pass through. This is the definitive physical sign of labour progression.

• Show: This is a blood-tinged mucoid discharge from the cervical canal. As the cervix dilates and effaces, small blood vessels in the cervix rupture, mixing with mucus to create the “show.”

• Rupture of Membranes (ROM): While membrane rupture can be a sign of labour, it is not always a definitive early sign. It can happen at various points – early in labour, later in the first stage, or even spontaneously at the time of birth. Therefore, it’s considered a less reliable early sign on its own.

Causes of Onset of Labour

The precise trigger for labour onset is not completely understood. It is believed to be a complex interaction of hormonal and mechanical factors.

Hormonal Factors

Theories regarding the hormonal initiation of labour include:

1. Oxytocin Stimulation Theory: As pregnancy advances, the uterus becomes increasingly sensitive to oxytocin, a hormone known to stimulate uterine contractions. While the exact mechanism of increased sensitivity isn’t fully clear, oxytocin’s role in labour is well-established.

2. Progesterone Withdrawal Theory: Progesterone plays a role in maintaining uterine relaxation during pregnancy. A decrease in progesterone levels towards the end of pregnancy may remove this uterine muscle relaxation, potentially stimulating the synthesis of prostaglandins and enhancing the effects of estrogen, which is known to stimulate uterine muscle activity.

3. Estrogen Stimulation Theory: Estrogen is thought to increase the irritability of uterine muscles, making them more prone to contractions. A rise in estrogen levels is believed to stimulate the uterine lining (decidua) to release prostaglandins. Both prostaglandins and oxytocin promote uterine contractions.

4. Fetal Cortisol Theory: The fetal adrenal glands release cortisol. This fetal cortisol is proposed to potentially affect maternal estrogen levels, contributing to the hormonal cascade leading to labour.

5. Prostaglandin Stimulation Theory: Prostaglandins are hormone-like substances that can stimulate smooth muscle contraction. Their release in the uterus is considered a key factor in initiating labour contractions.

It’s most likely that a combination of these hormonal mechanisms working in concert initiates labour.

Mechanical Factors

Mechanical factors proposed to contribute to labour onset include:

1. Overstretching and Overdistension of the Uterus: The physical stretching of the uterus as the baby grows to term may reach a threshold that triggers contractions.

2. Pressure on Cervical Nerve Endings: As the baby’s presenting part (usually the head) descends and applies pressure on nerve endings in the cervix, it can stimulate the cervical nerve plexus (cervical ganglion). This stimulation may play a role in triggering labour.

3. Increased Braxton Hicks Contractions: The increasing strength and frequency of Braxton Hicks contractions in late pregnancy may act as a preparatory phase, potentially leading to the initiation of true labour.

Stages of Labour

Labour is divided into four stages:

1. First Stage:

   • Begins with the onset of regular, rhythmic uterine contractions and concludes when the cervix is fully dilated (approximately 10cm).

   • This stage is primarily focused on cervical dilation.

   • It is further subdivided into three phases:

     • Latent Phase: Period of slow cervical dilation, from 0 to 3cm. Can last 6-8 hours or longer, especially for first-time mothers (nulliparous).

     • Active Phase: Phase of more rapid cervical dilation, from 4cm to 8cm.

     • Transitional Phase: From 8cm cervical dilation to full cervical dilation (10cm), marking the end of the first stage.

2. Second Stage:

   • This is the stage of fetal expulsion.

   • It begins once the cervix is fully dilated and ends with the complete birth of the baby.

   • Also divided into two phases:

     • Propulsive Phase: Starts at full cervical dilation and lasts until the baby’s presenting part descends to the pelvic floor.

     • Expulsive Phase: Characterized by the mother’s active bearing down efforts (pushing) in response to contractions and the urge to push, culminating in the delivery of the baby.

3. Third Stage:

   • This stage involves the separation and expulsion of the placenta and fetal membranes, as well as management of postpartum bleeding.

   • It begins immediately after the birth of the baby and ends with the expulsion of the placenta and membranes.

   • Typically lasts 5-30 minutes. With active management of the third stage (e.g., oxytocin administration, controlled cord traction), it is often completed within 5-15 minutes.

4. Fourth Stage:

   • Often referred to as the recovery stage or immediate postpartum period.

   • Defined as the first hour after delivery of the placenta. This is a critical period for monitoring both the mother and the newborn for any immediate postpartum complications, such as excessive bleeding in the mother or adaptation of the newborn to extrauterine life.