INSTRUMENTAL DELIVERY AND THE RISKOF AVULSION: A META- ANALYSIS
T. FRIEDMAN, G. D. ESLICK, H.DIETZ;
Sydney Med. Sch. Nepean, Sydney, Australia.
Introduction: Female pelvicorgan prolapse (FPOP) is a common condition, associated withsignificant impairment in overall quality of life (1), with alifetime risk for surgery of 10-20%. The aetiology is not fullyunderstood. The most significant risk factor is vaginal delivery(2),especially for bladder and uterine prolapse, partly mediated throughlevator muscle trauma (3). It is generally assumed that levatormuscle injury incidence is higher in instrumental delivery,especially when forceps is involved. However, we have not been ableto identify a meta- analysis on this issue.
Objective: Toperform a systematic review and quantitative meta-analysis in orderto determine the risk of levator muscle avulsion after normaldelivery, as well as the added risk following Forceps and Vacuumassisted birth.
Methods: Four electronic databases weresearched for studies published between 1991 and June 1st2016 with no language restrictions. From 555 citations identified, atotal of 23 studies met our inclusion criteria. We included studiesthat met the following criteria: (1) Levator muscle avulsion wasrecognized after vaginal delivery; (2) the risk point estimate wasreported as an odds ratio (OR), or the data was presented such thatan OR could be calculated; (3) the 95% confidence interval (CI) wasreported, or the data was presented such that the CI could becalculated; (4) an internal comparison was used when calculating therisk estimate.
Results: Overall 23 studies met ourinclusion criteria, and 14 of those were prospective. 9 studies weredone in Europe, 4 in America, 5 in Asia and 5 in Australia. 20 usedultrasound for the diagnosis of avulsion, and 3 were based on MRimaging. The average incidence of levator avulsion among NVD was14.9% (6.2-33.3%), among forceps deliveries 55.5% (22-89%), and amongvacuum deliveries 18% (0-41%). Three types of comparison wereperformed according to data availability: firstly, Forceps versusvacuum, secondly, Forceps versus NVD, and thirdly, Vacuum versus NVD.The first meta-analysis showed an increased risk for avulsionfollowing forceps delivery compared with vacuum delivery with an oddsratio (OR) of 4.45 and a confidence interval (CI) of 3.09-6.42, p<0.01. The second meta-analysis showed an increased risk foravulsion following forceps delivery compared with NVD with an OR of7.02 95% CI 5.04-9.78, p value <0.01. The third meta-analysisshowed an increased risk for avulsion following vacuum deliverycompared with NVD with an OR of 1.27 95% CI 0.97-1.67, p value 0.09.
Figure 1: Avulsion after Forceps(n=364 ) versus Vacuum (n= 613)
Figure 2: Avulsion after Forceps(n=388) versus NVD (n=2248)
Conclusions: This meta-analysisis consistent with the hypothesis that forceps is a statisticallysignificant risk factor for levator muscle avulsion, at an OR of 7.02(5.04-9.78) compared to NVD and an OR of 4.45 (3.09-6.42) compared toVacuum. The latter seems to be a weak risk factor for avulsion, witha lower OR of 1.27 (0.97-1.67) which did not reach statisticalsignificance.
References: 1. Obstet Gynecol2009;113(3):609.
2. BJOG 2013;120(2):152-60.