title: Head-to-body delivery interval using 'two-step' approach in vaginal deliveries: effect on umbilical artery pH.
abstract: OBJECTIVE
  To assess the duration of head-to-body interval using a 'two-step' approach to delivery that include waiting for the next contraction to deliver the shoulders; and its effect on umbilical artery pH and neonatal outcome.
  
  
  METHODS
  Prospective observational study on vaginal deliveries with singleton cephalic fetuses at term from June to December 2005. Clinical variables were evaluated in reference to umbilical artery pH and evidence of neonatal acidemia, defined as pH  ≤ 7.10 or base excess (BE) ≤ -12 in a multivariate model.
  
  
  RESULTS
  Head-to-body interval was timed and recorded in 789 deliveries. The mean head-to-body interval was 88 ± 61 s. Although head-to-body interval was significantly correlated to umbilical artery pH (p = 0.02), the decline in umbilical artery pH in relation to the head-to-body interval was clinically not significant (0.0078 units for every additional minute of the interval). At the multivariate analysis, umbilical artery pH  ≤ 7.10 and/or BE  ≤ -12 were significantly related to abnormal fetal heart rate tracing during the second stage (p = 0.012) and operative vaginal delivery (p = 0.045), but not to head-to-body interval (p = 0.25). Shoulder dystocia occurred in three cases (0.38%).
  
  
  CONCLUSIONS
  A 'two-step' approach to birth does not significantly increase the risk of neonatal acidemia.
authors.affiliation: Department of Obstetrics and Gynecology, San Gerardo Hospital, University of Milano-Bicocca, Monza, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Locatelli
authors.forename: Maddalena
authors.initials: M
authors.lastname: Incerti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ghidini
authors.forename: Anna
authors.initials: A
authors.lastname: Longoni
authors.forename: Giovanna
authors.initials: G
authors.lastname: Casarico
authors.forename: Simona
authors.initials: S
authors.lastname: Ferrini
authors.forename: Nicola
authors.initials: N
authors.lastname: Strobelt
mesh_terms: D000138:Acidosis / Q000097:blood / Q000453:epidemiology; D000328:Adult; D036861:Delivery, Obstetric / Q000379:methods* / Q000706:statistics & numerical data; D004420:Dystocia / Q000453:epidemiology; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D006257:Head; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D011247:Pregnancy; D012782:Shoulder; D013997:Time Factors; D014469:Umbilical Arteries / Q000737:chemistry*; D014621:Vagina