A randomised controlled trial of two instruments for vacuum‐assisted delivery (Vacca Re‐Usable OmniCup and the Bird anterior and posterior cups) to compare failure rates, safety and use effectiveness

Abstract

Most previous trials of vacuum-assisted delivery have been in settings with high rates of instrumental vaginal delivery (8-12%) and high rates of failure to deliver with the intended instrument (20-30%). Over the past 20 years, vacuum-assisted delivery rates at the Port Moresby General Hospital have been 3-4% with failure rates of <3%. The objective is to compare the failure rates of two vacuum extractor instruments, the Vacca Re-Usable Omnicup and the Bird Vacuum delivery system (anterior and posterior cups). Port Moresby General national referral and teaching Hospital (PMGH), Papua New Guinea. Two hundred consecutive women requiring assisted delivery, June-December, 2007. When a woman required an assisted delivery, she was randomised into either the Vacca Re-Usable Omnicup (Clinical Innovations Inc.) or Bird anterior or posterior metal cup (depending upon the position of the vertex). One hundred women were randomised to each vacuum device. Statistical analysis was on 'an intention-to-treat' basis. The main outcome measure was the successful completion of the delivery with the allocated instrument. Secondary outcomes were maternal trauma (episiotomy and trauma to the maternal genital tract), significant scalp trauma (sub-galeal haemorrhage or serious abrasion) and fetal and neonatal outcomes (Apgar score less than seven at 5 minutes, days spent in the Special Care Nursery and neonatal death). Failure rates for both Omnicup (2/100) and Bird metal cups (6/100) were not statistically different (RR 1.05, 95% CI 0.99-1.12; P = 0.17). Rates of maternal trauma and fetal scalp trauma were similar in both groups. Both the Vacca re-useable Omnicup and the Bird metal cups are very effective instruments to achieve successful assisted delivery and equally so. Failures and problems were associated with not applying the vacuum cup to the flexion point on the fetal scalp and the mechanical faults with vacuum equipment devices.