38 Based on these and similar data,39,40 it is generally recommended that vacuum-assisted deliveries be achieved with no more than 3 sets of pulls and a maximum of 2 to 3 cup detachments (pop-offs). The total vacuum application time should be limited to 20 to 30 minutes.4 These recommendations are based more upon common sense and Volasertib leukemia experience than scientific data as observational series have shown no long-term differences in neonatal outcome related to these variables.25 Reasons for Failed Vacuum Extraction Vacuum-assisted vaginal deliveries may fail because of poor patient selection (such as attempting vacuum extraction in pregnancies complicated by cephalopelvic disproportion) or errors in application or technique.

For example, selection of the incorrect cup size, accidental inclusion of maternal soft tissues within the cup, and/or incorrect placement of the vacuum cup, resulting in worsening asynclitism (lateral traction) or de-flexion (extension) of the fetal head, may all contribute to failed vacuum attempts. Failure to apply traction in concert with maternal pushing efforts or traction along the incorrect plane may also result in failed vacuum extraction. To avoid fetal injury, the obstetric care provider should not be overly committed to achieving a vaginal delivery and should be willing to abandon the procedure if it is not progressing well. Delay may increase the risk of neonatal or maternal morbidity. The ability to perform an emergency cesarean delivery should always be at hand.

Maternal Complications There is substantial evidence that instrumental deliveries increase maternal morbidity, including perineal pain at delivery, pain in the immediate postpartum period, perineal lacerations, hematomas, blood loss and anemia, urinary retention, and long-term problems with urinary and fecal incontinence. A randomized trial of 118 nulliparous term deliveries showed significant maternal soft tissue trauma in 48.9% of forceps deliveries, 36.1% of deliveries using the silastic vacuum extractor, and 21.6% of deliveries using the Mityvac? vacuum extractor (CooperSurgical, Trumball, CT) deliveries.41 Another review of over 50,000 vaginal deliveries at the University of Miami reported that the rates of third and fourth degree perineal lacerations were higher in vacuum-assisted (10%) and forceps deliveries (20%) compared with spontaneous vaginal deliveries (2%).

42 The highest rates of maternal perineal trauma are associated with deliveries involving rotations larger than 45�� and with midforceps procedures.43 The risk of maternal trauma is higher for fetuses in the occiput-posterior position.44,45 For example, a retrospective cohort study Carfilzomib of over 390 vacuum-assisted vaginal deliveries found that an occiput-posterior position was associated with a 4-fold increased risk of anal sphincter injury compared with an occiput-anterior position, which persisted after controlling for multiple covariables.