Vacuum-assisted delivery.

Unsuccessful vacuum extraction, cup detachment and failed anterior rotation in occipitoposterior positions are commonly associated with obstetric factors that are avoidable or correctable. These factors include the preferential use of soft vacuum cups, incorrect cup applications and attempts to deliver with the vacuum extractor before the cervix is completely dilated. Evidence from randomized trials demonstrates that soft cups cause fewer cosmetic effects and scalp lacerations than rigid cups. Soft cups do not reduce the incidence of cephalhaematomas nor have they been shown to provide any advantage over rigid cups for the prevention of subgaleal haemorrhage. Clinically significant subgaleal haemorrhage and intracranial injury are almost always preceded by difficult vacuum extraction. Although the vacuum extractor is less likely than forceps to injure the mother's genital tract and anal sphincters at delivery, no significant differences have been demonstrated between the instruments in terms of subsequent urinary or bowel disturbances.