Choice of instruments for assisted vaginal delivery.

BACKGROUND: Instrumental or assisted vaginal birth is commonly used to expedite birth for the benefit of either mother or baby or both. It is sometimes associated with significant complications for both mother and baby. The choice of instrument may be influenced by clinical circumstances, operator choice and availability of specific instruments.

OBJECTIVES: To evaluate different instruments in terms of achieving a vaginal birth and avoiding significant morbidity for mother and baby.

SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2010).

SELECTION CRITERIA: Randomised controlled trials of assisted vaginal delivery using different instruments.

DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trial quality, extracted the data, and checked them for accuracy.

MAIN RESULTS: We included 32 studies (6597 women) in this review. Forceps were less likely than the ventouse to fail to achieve a vaginal birth with the allocated instrument (risk ratio (RR) 0.65, 95% confidence interval (CI) 0.45 to 0.94). However, with forceps there was a trend to more caesarean sections, and significantly more third- or fourth-degree tears (with or without episiotomy), vaginal trauma, use of general anaesthesia, and flatus incontinence or altered continence. Facial injury was more likely with forceps (RR 5.10, 95% CI 1.12 to 23.25). Using a random-effects model because of heterogeneity between studies, there was a trend towards fewer cases of cephalhaematoma with forceps (average RR 0.64, 95% CI 0.37 to 1.11).Among different types of ventouse, the metal cup was more likely to result in a successful vaginal birth than the soft cup, with more cases of scalp injury and cephalhaematoma. The hand-held ventouse was associated with more failures than the metal ventouse, and a trend to fewer than the soft ventouse.Overall forceps or the metal cup appear to be most effective at achieving a vaginal birth, but with increased risk of maternal trauma with forceps and neonatal trauma with the metal cup.

AUTHORS' CONCLUSIONS: There is a recognised place for forceps and all types of ventouse in clinical practice. The role of operator training with any choice of instrument must be emphasised. The increasing risks of failed delivery with the chosen instrument from forceps to metal cup to hand-held to soft cup vacuum, and trade-offs between risks of maternal and neonatal trauma identified in this review need to be considered when choosing an instrument.