title: Timing of operative vaginal delivery and associated perinatal outcomes in nulliparous women.
abstract: OBJECTIVE
  To compare perinatal outcomes in nulliparous women who had operative vaginal delivery early during second stage (1-3 h) to those who delivered vaginally with a prolonged second stage (>3 h).
  
  
  METHODS
  This is a retrospective cohort study of nulliparas with term, singleton, vaginal deliveries beyond the first hour of second stage. Women who underwent operative vaginal deliveries (OVD) during 1-3 h of the second stage were compared to women who delivered vaginally but with a second stage duration of >3 h. Perinatal outcomes were examined using chi-square test, and potential confounders were controlled for using multivariable logistic regression analysis.
  
  
  RESULTS
  Nulliparas delivered vaginally beyond 3 h of second stage had lower odds of third or fourth degree perineal lacerations (aOR = 0.63, 95% CI 0.51-0.77), neonatal cephalohematoma (aOR = 0.48, 95% CI 0.28-0.83) and admissions to intensive care nursery (aOR = 0.70, 95% CI 0.49-0.99) compared to operative vaginal deliveries during 1-3 h of second stage.
  
  
  CONCLUSIONS
  Compared to nulliparas who had operative vaginal deliveries performed early (1-3 h) in the second stage, women who delivered later (>3 h duration of second stage), either by spontaneous or operative vaginal delivery, had lower risk of third or fourth degree perineal lacerations without incurring risk of increased adverse neonatal outcomes.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California 94143-0132, USA. yvecheng@hotmail.com
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Cheng
authors.forename: Brian L
authors.initials: BL
authors.lastname: Shaffer
authors.forename: Katherine
authors.initials: K
authors.lastname: Bianco
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Caughey
mesh_terms: D000328:Adult; D036861:Delivery, Obstetric / Q000009:adverse effects* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007748:Labor Stage, Second; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D013997:Time Factors