Describe ventouse — its aetiology, clinical features and management.

Definition

The ventouse (vacuum extractor) delivers the fetal head by traction applied through a cup held to the scalp by negative pressure (vacuum). The suction draws up an artificial caput (the "chignon") within the cup.

Indications

Delay in the second stage, maternal exhaustion, and to assist delivery when bearing-down is contraindicated (though forceps is preferred when rapid delivery is essential).

Prerequisites and Contraindications

Similar to forceps (engaged head, known position, ruptured membranes, no disproportion, empty bladder). It requires maternal effort and a gestation of ≥ 34 weeks. Contraindicated in face/breech presentation, prematurity (< 34 weeks), suspected fetal coagulopathy or bony disease, and marked caput.

Advantages Over Forceps

• Less maternal genital-tract trauma and usually no need for general/regional block.
• Occupies less space; allows auto-rotation of the head.

Conduct of the Procedure

The cup is applied over the flexion point on the fetal scalp; a vacuum of about 0.6–0.8 kg/cm² is built up, and traction is applied during contractions synchronised with maternal bearing-down, along the axis of the birth canal. The cup is released once the head is delivered.

Disadvantages / Complications

• Slower; fails if uterine contractions or maternal effort are poor.
• Fetal scalp injuries, cephalhaematoma, subgaleal haemorrhage and retinal haemorrhage; the chignon resolves spontaneously.

A Note on WHY the Ventouse Needs Maternal Effort

A useful contrast is understanding why the ventouse and the forceps are not simply interchangeable. The ventouse works by applying a vacuum cup to the fetal scalp over the flexion point, so that traction — applied in time with a contraction and with the mother's bearing-down effort — promotes flexion and descent. It is therefore an assisting instrument: it augments the mother's expulsive efforts rather than replacing them, and it will fail (the cup detaching) if excessive force is used. The implications are clear. It is unsuitable where the mother cannot push (an exhausted or anaesthetised woman, or one with heart disease in whom bearing down must be avoided), where speed is essential (severe fetal distress), and where the fetal head is fragile or the scalp cannot withstand the vacuum — hence its avoidance in prematurity (below 34 weeks), face presentation and the after-coming head of a breech. In these situations forceps are used. Its compensating advantages are that it needs less space in the vagina and causes markedly less maternal perineal and vaginal trauma. The price is paid by the fetus: chignon (harmless), cephalhaematoma, scalp lacerations, retinal haemorrhage and, rarely, a dangerous subgaleal haemorrhage.

Contraindicated in preterm and face presentation.

• The ventouse delivers by traction on a vacuum cup applied over the flexion point — assisting, not replacing, the mother's expulsive effort.
• Advantages over forceps: less maternal trauma, less analgesia and less space needed; the head may be delivered with mild deflexion or rotation.
• Contraindicated in prematurity (<34 weeks), face presentation, the after-coming head of a breech, and when the mother cannot push or speed is essential.
• Fetal complications: chignon (harmless), cephalhaematoma, scalp laceration, retinal haemorrhage, subgaleal haemorrhage (dangerous).
• Abandon the attempt if the cup detaches repeatedly or there is no descent after three pulls — proceed to caesarean.