Pressure is applied inward and downward until contact is made with the fetal scalp. The cup should be placed over the posterior fontanelle. A finger is swept around the cup to make sure no maternal tissue is within the cup. Suction pressure is raised to 100 mm Hg, and the location of the cup is rechecked. With the onset of a contraction, suction pressure is raised to a range of 380 to 580 mm Hg.
Traction is applied perpendicularly to the cup, in line with the maternal axis.
Should the cup be dislodged, the fetal scalp is to be checked before the cup is reapplied. When the contraction subsides, the suction pressure is reduced to 100 mm Hg. The sequence is repeated with each contraction. More than three good attempts are not recommended unless progress is being made. As the head crowns, an episiotomy may be cut.