Preconditions: The cervix must be fully dilated, the baby’s head engaged and position known, membranes ruptured, and facilities available for immediate caesarean section if required.
Traction limits: Guidance recommends no more than three pulls (tractions) with either vacuum or forceps, and progress should be seen with each pull. If there is no descent after three pulls, the attempt should be abandoned.
Sequential use: Switching from vacuum to forceps (or vice versa) greatly increases the risk of head and brain injuries and is generally regarded as unsafe.