title: Comparison of active phase labor between triplet, twin, and singleton gestations.
abstract: OBJECTIVE
  To characterize the active phase of labor in triplet pregnancies and compare it with gestational age-matched twins and singletons.
  
  
  METHODS
  Active phase rates were calculated beginning at 5 cm of dilation for women with triplet gestations longer than 24 weeks who labored and reached the second stage. Twin and singleton cohorts that also completed the first stage of labor were matched for gestational age at delivery (+/-1 week), parity, and epidural use. Intrapartum variables included oxytocin use (induction or augmentation, duration of infusion, and maximum dosage), cervical dilation at membrane rupture, and active phase dilation rate.
  
  
  RESULTS
  Thirty-two triplet pregnancies met inclusion criteria between January 1994 and September 1998 and were each compared with twin and singleton cases in a 1:2 ratio. Triplet and twin active phase rates, while similar (1.8 versus 1.7 cm/hour, respectively), were significantly lower than the mean singleton dilation rate (2.3 cm/hour, P =.02). No other intrapartum variables differed between the three groups. Despite controlling for gestational age at delivery, mean birth weights were significantly higher in singletons and correspondingly lower in twins and triplets (2,493 versus 2,112 and 1,968 g, respectively; P =.001). An analysis of active phase dilation rates as a function of the cumulative birth weight per pregnancy demonstrated an inverse correlation, with slower progress in active labor associated with increasing total fetal weight (R = -.24; P =.002).
  
  
  CONCLUSIONS
  Triplet and twin active phase dilation proceeds at a slower rate than that observed in singleton pregnancies. The rate of active phase dilation is inversely correlated to total fetal weight.
authors.affiliation: Division of Maternal-Fetal Medicine, Evanston & Prentice Womens' Hospitals, Northwestern University Medical School, Chicago, Illinois, USA. r-silver@nwu.edu
authors.forename: R K
authors.initials: RK
authors.lastname: Silver
authors.forename: E I
authors.initials: EI
authors.lastname: Haney
authors.forename: W A
authors.initials: WA
authors.lastname: Grobman
authors.forename: S N
authors.initials: SN
authors.lastname: MacGregor
authors.forename: H L
authors.initials: HL
authors.lastname: Casele
authors.forename: M G
authors.initials: MG
authors.lastname: Neerhof
mesh_terms: D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology*; D011247:Pregnancy; D012044:Regression Analysis; D013997:Time Factors; D014310:Triplets; D014427:Twins