title: Does vacuum delivery carry a higher risk of shoulder dystocia? Review and meta-analysis of the literature.
abstract: BACKGROUND
  Vacuum extractor has been increasingly used over the last decades and is acknowledged as a risk factor for shoulder dystocia (SD). In this meta-analysis we assess the actual risk of SD following a vacuum delivery compared to spontaneous vaginal delivery (SVD) and forceps.
  
  
  METHODS
  Systematic literature search (English literature only) on MEDLINE, EMBASE, ScienceDirect, the Cochrane library and ClinicalTrials.gov conducted up to May 2015. Key search terms included: Operative/Vacuum/Forceps delivery [Mesh] and shoulder dystocia and subheadings. 2 stage-process study selection. We included only studies where data concerning the occurrence of SD following operative vaginal delivery were reported as adjusted odds ratio (AOR) and no significant difference in confounding factors for SD was recorded. Included trials clustered according to the delivery mode (1) vacuum vs. SVD, (2) forceps vs. vacuum. Methodological quality of each study evaluated with the Newcastle-Ottawa System (NOS).
  
  
  RESULTS
  87 potentially relevant papers. After applying inclusion and exclusion criteria only 7 were selected for the meta-analysis. Vacuum delivery appeared associated with a higher risk of SD than SVD in both fixed and random model (OR 2.87 and 2.98 respectively). No difference in the rate of SD was found between vacuum and forceps (p>0.05).
  
  
  CONCLUSIONS
  Vacuum extractor carries an increased risk of SD compared with spontaneous vaginal delivery whereas the occurrence of SD does not seem to vary following vacuum or forceps.
authors: Department of Surgical Sciences, Obstetrics and Gynecology Unit, University of Parma, Parma, Italy. Electronic address: andrea.dallasta1@gmail.com.
authors: Andrea
authors: A
authors: Dall'Asta
authors: Department of Surgical Sciences, Obstetrics and Gynecology Unit, University of Parma, Parma, Italy. Electronic address: tullio.ghi@unipr.it.
authors: Tullio
authors: T
authors: Ghi
authors: Department of Neuroscience, University of Parma, Parma, Italy. Electronic address: giuseppe.pedrazzi@unipr.it.
authors: Giuseppe
authors: G
authors: Pedrazzi
authors: Department of Surgical Sciences, Obstetrics and Gynecology Unit, University of Parma, Parma, Italy. Electronic address: fruscatiziana@gmail.com.
authors: Tiziana
authors: T
authors: Frusca
mesh_terms: D004420:Dystocia / Q000209:etiology*; D005260:Female; D006801:Humans; D009772:Obstetrical Forceps / Q000009:adverse effects; D011247:Pregnancy; D012307:Risk Factors; D012782:Shoulder; D014620:Vacuum Extraction, Obstetrical / Q000009:adverse effects*
keywords: Forceps; Labor complication; Operative delivery; Shoulder dystocia; Vacuum extractor