title: Progression of labor in twin versus singleton gestations.
abstract: OBJECTIVE
  The aim of this study was to investigate whether labor curves of twin gestations differ from those of singleton gestations.
  
  
  METHODS
  Among 1821 twin deliveries at our institution (1984-1996), we found 69 nulliparous and 94 multiparous women who were delivered at term (>/=37 weeks) of a vertex twin A with a birth weight of >/=2500 g. We excluded women who had any of the following: induction of labor, oxytocin augmentation, cervical dilatation >6 cm on admission, tocolysis during the previous 14 days, height <150 cm, hypertension, and diabetes. Women with singleton gestations (n = 163) who met the same exclusion criteria were matched for parity and maternal age (+/-3 years). Stage 1 of labor was defined as the interval between 4 and 10 cm cervical dilatation. Kaplan-Meier survival analysis was used for comparison between the groups.
  
  
  RESULTS
  The study and control groups were similar in mean maternal height; however, women with twins were significantly heavier than were those with singletons (79.3 +/- 11.2 kg vs 73.2 +/- 10.8 kg, P <.001), had a higher frequency of epidural anesthesia (82% vs 62%), and had a significantly lower birth weight of the presenting fetus (2779.1 +/- 242.5 g vs 3301.4 +/- 429.2 g, P <.001). The cervical effacements and vertex stations on admission were similar in the 2 groups. On admission the cervical dilatation of women delivered of twins was smaller than that of the control group. Twin gestations had a significantly shorter first stage of labor than did their matched singleton control gestations (3.0 +/- 1.5 hours vs 4.0 +/- 2. 6 hours, P <.0001). This difference was apparent only in nulliparous women. No statistical difference was noted in the mean length of the second stage of labor (0.8 +/- 0.5 hour for twins and 0.7 +/- 0.6 hour for singletons).
  
  
  CONCLUSIONS
  Twin gestations have a significantly shorter first stage of labor than do singleton gestations. This difference may be the result of the birth weight of the presenting twin being lower than that of its singleton counterpart or to differences in uterine contractility in twin and singleton gestations. Different labor curves should be considered for managing twin deliveries.
authors.affiliation: Departments of Obstetrics and Gynecology and Epidemiology, Sheba Medical Center, Oregon Health Sciences University, Portland, Oregon, USA.
authors.forename: E
authors.initials: E
authors.lastname: Schiff
authors.forename: S B
authors.initials: SB
authors.lastname: Cohen
authors.forename: M
authors.initials: M
authors.lastname: Dulitzky
authors.forename: I
authors.initials: I
authors.lastname: Novikov
authors.forename: S A
authors.initials: SA
authors.lastname: Friedman
authors.forename: S
authors.initials: S
authors.lastname: Mashiach
authors.forename: S
authors.initials: S
authors.lastname: Lipitz
mesh_terms: D000328:Adult; D020070:Cervical Ripening / Q000502:physiology; D005260:Female; D006801:Humans; D007747:Labor Stage, First / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D011272:Pregnancy, Multiple / Q000502:physiology*; D016019:Survival Analysis; D013997:Time Factors; D014427:Twins