Once the ventouse is in position, the rubber tube attached to the cup is connected to the suction. This can be a suction unit installed on the wall of the hospital delivery room, or a manual handheld pump. The negative pressure (or 'vacuum') is created as the cup is held in place. A monometer attached to the suction lets the caregiver know the level of pressure being created. It will start at about 0.2 kg/cm2 and generally increase every 1 minute, until a maximum of 0.8 kg/cm2 is reached.
With the pressure achieved, the caregiver will wait for the next contraction. If you have an epidural in place, the midwife will feel your belly and let the doctor know when a contraction begins. You will then be asked to push while the doctor pulls. Once the contraction eases off, you will be told to stop pushing. It will usually take more than one contraction to deliver your baby.
If the baby's head is high in the birth canal, your caregiver will use downward traction until the baby's head can be felt below the symphysis pubis. As the head starts moving up under the symphysis pubis, upward traction is used. As the upward traction is commenced, the perineum starts to stretch, and the head will start to emerge.
Once the baby's head is delivered, the pressure is released slowly from the cup (to reduce any risk of injury to the baby's scalp) and the cup is removed. The baby's body is then delivered in the usual way.
Guidelines for safe use
The use of a ventouse has guidelines for caregivers for their safe use. If the ventouse cannot be used within these guidelines, then it will be abandoned, and forceps will then be tried. If the forceps are unsuccessful, then a Caesarean will be needed.
The guidelines include: