Objective: To examine the association between uterine rupture and oxytocin
use in trial of labor after cesarean.
Methods: A case-control study was performed. Cases were all women with uter
ine ruptures who received oxytocin during a trial of labor after a single c
esarean delivery within a 12-year period (n = 24). Four controls undergoing
trial of labor after a single cesarean delivery were matched to each case
by 500 g birth weight category, year of birth, and by induction or augmenta
tion (n = 96). The study had an 80% power to detect a 40% increase in oxyto
cin duration or a 65% increase in total oxytocin dose.
Results: No significant differences were seen in initial oxytocin dose, max
imum dose, or time to maximum dose. Although women with uterine ruptures ha
d higher exposure to oxytocin as measured by mean total oxytocin dose (544
mU higher) and oxytocin duration (54 minutes longer), these differences wer
e not statistically significant. Women with uterine rupture who received ox
ytocin were more likely to have experienced an episode of uterine hyperstim
ulation (37.5% compared with 20.8%, P = .05). However, the positive predict
ive value of hyperstimulation for uterine rupture was only 2.8%.
Conclusion: Although no significant differences in exposure to oxytocin wer
e detected between cases of uterine rupture and controls, the rarity of ute
rine rupture limited our power to detect small differences in exposure. In
women receiving oxytocin, uterine rupture is associated with an increase in
uterine hyperstimulation, but the clinical value of hyperstimulation for p
redicting uterine rupture is limited. (C) 2001 by The American College of O
bstetricians and Gynecologists.