Tachysystole in term labor: incidence, risk factors, outcomes, and effect on fetal heart tracings

Am J Obstet Gynecol. 2013 Jul;209(1):32.e1-6. doi: 10.1016/j.ajog.2013.04.004. Epub 2013 Apr 6.


Objective: Recent recommendations called for obstetricians to abandon the terms of "hyperstimulation" and "hypercontractility" in favor of the more rigidly defined term, "tachysystole" (TS). The aim of the current study is to describe incidence of and risk factors for TS, describe fetal heart rate (FHR) changes associated with TS, and investigate maternal and neonatal outcomes associated with TS.

Study design: For this retrospective cohort study, we reviewed and analyzed the intrapartum FHR and tocometric characteristics of all patients with a singleton, nonanomalous fetus in term labor in a single hospital system over a 28-month period. Univariate association testing was done using χ(2) and t tests, comparing demographics, pregnancy characteristics, outcomes, and TS events. Multivariable association testing between risk factors and TS events were tested using generalized estimating equations, adjusting for multiple pregnancies during the study period for the same woman.

Results: There were a total of 50,335 deliveries from 48,529 women during the 28-month period. Of these, there were a total of 7567 TS events in 5363 deliveries among 5332 women. Use of oxytocin or misoprostol, an epidural, hypertension, and induction of labor were associated with an increased risk of TS. We found a doubling of TS events with any oxytocin, a dose-response correlation between oxytocin and TS, FHR changes occurring in a quarter of TS events and, finally, that presence of TS increases the chance of composite neonatal morbidity.

Conclusion: TS is associated with specific risk factors and impacts FHR and neonatal morbidity.

Keywords: contractions; fetal heart tracing; hyperstimulation; labor; tachysystole.

MeSH terms

  • Adult
  • Cesarean Section / statistics & numerical data
  • Female
  • Fetal Monitoring
  • Heart Rate, Fetal / drug effects
  • Heart Rate, Fetal / physiology*
  • Humans
  • Incidence
  • Misoprostol / adverse effects*
  • Obstetric Labor Complications / epidemiology
  • Obstetric Labor Complications / etiology*
  • Oxytocics / adverse effects*
  • Oxytocin / adverse effects*
  • Pregnancy
  • Pregnancy Outcome / epidemiology
  • Retrospective Studies
  • Risk Factors
  • Uterine Contraction / drug effects
  • Uterine Contraction / physiology*
  • Uterine Monitoring


  • Oxytocics
  • Misoprostol
  • Oxytocin