title: Intertwin time interval: how it affects the immediate neonatal outcome of the second twin.
abstract: OBJECTIVE
  Customarily 30 minutes is used as the upper limit of intertwin birth times. This study was conducted to define factors that influence the immediate neonatal outcome of the second twin and to assess whether a valid cutoff time is evident.
  
  
  METHODS
  We evaluated all live born viable vaginal twin deliveries (144) between November 1997 and December 2003. The relationship between intertwin birth time and neonatal outcome was then evaluated continuously and in 15 to 30-minute intervals.
  
  
  RESULTS
  In multivariate analysis, only intertwin birth time predicted umbilical cord pH. Arterial/venous pH decreased linearly at a rate of 0.00063 and 0.00081 U/min. Venous pH was significantly lower in later 15-minute intervals compared with earlier ones (P = .002), and in patients delivering before or after a 30-minute cutoff (7.31 vs 7.26, P = .012).
  
  
  CONCLUSIONS
  Our study confirmed that longer intertwin birth time is associated with a continuous slow decline in umbilical cord pH. However, the small differences in pH were not large enough to impact clinical management.
authors.affiliation: Department of Obstetrics and Gynecology, William Beaumont Hospital, Royal Oak, Mich, USA. capricemcgrail@hotmail.com
authors.forename: Caprice D
authors.initials: CD
authors.lastname: McGrail
authors.forename: David R
authors.initials: DR
authors.lastname: Bryant
mesh_terms: D001034:Apgar Score; D001724:Birth Weight; D036861:Delivery, Obstetric; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn / Q000502:physiology*; D015999:Multivariate Analysis; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D012189:Retrospective Studies; D013997:Time Factors; D014427:Twins; D014471:Umbilical Veins