Vacuum extraction is an unusual forceps delivery for similar indications in the second stage of labor. The conditions that need to be satisfied for any instrumental delivery need to be checked prior to application. The cups come in different sizes and are usually 4 to 6 centimeters in diameter. The cup is applied over the flexion point which is 4 centimeters in front of the occiput on the midline indicated by sagittal suture. It is

halfway between the two parietal eminences and hence promotes flexion to permit the minimal diameters for the vertex to descend through the pelvis. Application over the flexion point is a flexing median application. At this site the anterior margin of the cup is 4 centimeters behind the posterior margin of the anterior fontanelle along the sagittal suture. If the position is close to the occiput but not on the midline it is called flexing paramedian application. If it is in the midline but closer to the anterior fontanelle it is deflexing median and if it is off the midline it is deflexing paramedian application. Deflexing applications expose larger diameters especially if they are paramedian applications.

It is essential for the man who is a midwife (accoucheur) for identification of the position of the head and to know whether the head is asynclitic so that the cup can be applied correctly over the flexion point. A specially designed cup is needed for occipito-lateral or posterior positions. The tubing should emerge from the lateral aspect of the cup or through a groove in the cup allowing the cup to be inserted and moved between the vaginal wall and the head to reach the flexion point. Soft silk, anterior metal cup or plastic cup where the tubing comes from the centre of the cup is suitable for application when the head is in the occipito-anterior position as the flexion point is within reach when the labia are parted and the cup is advanced on to the head. These cups are not suitable for occipito-posterior or lateral positions as the lateral vaginal wall would not permit the central stem or suction tubing on the dorsum of the cup for the cup to be shifted to the occiput. Once the cup is placed firmly on the fetal scalp vacuum is created by a hand held pump or a mechanical pump with negative pressure.

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