title: Outcome of attempted vaginal delivery after a previous vacuum extraction: a population-based study.
abstract: BACKGROUND
  Few studies have investigated long-term effects of a first vaginal instrumental delivery on subsequent mode of delivery. We investigated risks of repeat vacuum extraction and risk factors associated with a repeat vacuum extraction delivery.
  
  
  METHODS
  This is a population-based register study including 391 160 women with two consecutive singleton term (≥37 weeks) live births in cephalic presentation between/within the time period of 1992-2010 in Sweden. Rates and risk ratios of mode of delivery in second pregnancy in relation to primary mode of delivery were calculated using descriptive analyses and generalized linear models. Risk of repeat vacuum extraction was adjusted for maternal age and height, interpregnancy interval, gestational length, birthweight, induction, sex and occiput posterior position.
  
  
  RESULTS
  Compared with women with a primary spontaneous vaginal delivery, women with a primary vacuum extraction had an almost five-fold risk of vacuum extraction delivery and nearly a three-fold risk of emergency cesarean section at second delivery. For women with a primary emergency cesarean section, corresponding risks were substantially higher. Risk factors for a repeat vacuum extraction were increasing maternal age and an interpregnancy interval >4 years, decreasing maternal stature, increasing gestation length and birthweight, induction, giving birth to a male infant and occiput posterior position.
  
  
  CONCLUSIONS
  Nine of ten women who attempted a vaginal birth after a primary vacuum extraction succeeded in having a spontaneous vaginal delivery at second delivery. Compared with women with a primary spontaneous vaginal delivery, women with a primary vacuum extraction were at increased risk of repeat vacuum extraction and emergency cesarean section in subsequent delivery although their risk was not as high as that of women with a primary emergency cesarean section.
authors.affiliation: Department of Medicine, Division of Clinical Epidemiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Charlotte
authors.identifier: http://orcid.org/0000-0003-1401-1539
authors.initials: C
authors.lastname: Elvander
authors.affiliation: Department of Medicine, Division of Clinical Epidemiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Sven
authors.identifier: http://orcid.org/0000-0002-0805-8093
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D000328:Adult; D001721:Birth Intervals; D001724:Birth Weight; D001827:Body Height; D002585:Cesarean Section / Q000706:statistics & numerical data*; D036861:Delivery, Obstetric; D004630:Emergencies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007751:Labor, Induced / Q000706:statistics & numerical data; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D012042:Registries; D012307:Risk Factors; D013548:Sweden; D014620:Vacuum Extraction, Obstetrical / Q000706:statistics & numerical data*
keywords: Vacuum extraction; assisted delivery; mode of delivery; repeat instrumental delivery; subsequent delivery