The second stage of labour begins with full dilatation of cervix and ends with the expulsion of the fetus.

PHASES AND DURATION OF SECOND STAGE OF LABOUR

The average duration is estimated to be 2 hours in primigravidae and 30 minutes in multigravida.

The stages are two and include:

• Propulsive phase: From full dilatation until head touches the pelvic floor
• Expulsive phase: Since the time mother has irresistible desire to bear down and push until the baby is delivered

PHYSIOLOGY OF SECOND STAGE OF LABOUR

The physiological changes result from a continuation of some forces which have been at work during the first stage of labor and a complex interplay of hormones including oxytocin, adrenaline and endorphins. These movements include:

• Descend
• Uterine action
• Rupture of membrane
• Soft tissue displacement

Descend

Descend of the fetal presenting part which began during the first stage of labour and reaches its maximum speed toward the end of the first stage of labour, continues its rapid pace through the second stage of labour until the pelvic floor.

Uterine Action

Contractions during the second stage are frequent, strong and slightly longer that is approximately every 2 minutes, lasting for 60-90 seconds. They are strong in intensity and become expulsive in nature. In natural course of labour there is often a lull or quiet period between first and second stage. The woman rests and may even nap. The fetal head descends through the pelvis the contractions become more forceful and the woman begins to voluntarily bear down with expiratory, grunty short pushes.

Rupture of Membrane

The membrane often rupture spontaneously at the onset of the second stage. The consequent drainage of liquor allows the hard round fetal head to be directly applied to the vaginal tissue and aid distension.

Soft Tissue Displacement

As the hard fetal head descends the soft tissue of the pelvis become displaced. Anteriorly the bladder is pushed upwards into the abdomen where it is at less risk of injury during fetal descent. Posteriorly the rectum becomes flattened into the sacral curve and the pressure of the advancing head expels any residual fecal matter. The levator ani muscles dilates, thin out and become displaced laterally. The perineal body is flattened, stretched and thinned. The fetal head become visible at the vulva advancing and receding during resting phase until crowning.

Hormones

• Oxytocin: As the labor progresses and the baby descends through the birth canal, oxytocin promotes rhythmic, coordinated contractions of the uterine muscles, helping to push the baby downward and expel it from the uterus
• Adrenaline (Epinephrine): Pressure on the cervix and pelvic floor triggers the release of adrenaline. It increases the strength and frequency of contractions, providing the extra energy needed for pushing. It also helps the mother to stay focused and alert during the intense physical exertion of childbirth
• Endorphins: These are natural pain killers released by the body helping the mother cope up with the intense sensations of labor and birth. It promotes feelings of euphoria and well-being

SIGNS OF SECOND STAGE OF LABOUR

• Expulsive contractions and urge to bear down
• Sweating
• Rupture of membrane
• Dilatation and gaping of anus and perineal bulging
• Progressive visibility of fetal head at the introitus
• Congestion of the vulva

MANAGEMENT OF SECOND STAGE OF LABOR

The Aims and Principles:

• To achieve delivery of a normal healthy child with minimal physical and psychological maternal effects
• Early anticipation, recognition and management of any abnormalities during labour course
• To prevent perineal tears
• To assist in the natural expulsion of the fetus slowly and steadily

General Measures

• The patient should be in bed
• Constant supervision
• Vaginal examination
• Preparation of equipment {should be on standby}

Position During Labor

• Standing supported squat
• Semi sitting
• Squatting
• Side lying
• Leaning or kneeling forward with support
• Knee chest
• Common position of labor: Lithotomy