What to Know About Uterine Tachysystole

Woman in labor

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When you are waiting to meet your little one and for labor and delivery to begin, you likely have contractions on your mind. Toward the end of pregnancy, you second guess if every little cramp is a contraction.

As your due date draws near, you wonder if your contractions are signs of “false labor” or if they are “real” contractions. As early labor ramps up, you wonder if your contractions are becoming frequent enough to head to the hospital.

Once you are having regular contractions, you hope they are doing the work of dilating your cervix and allowing your baby to descend through the birth canal.

Yes, contractions can be uncomfortable and painful (to put it mildly!), but in a normally progressing vaginal birth, they are something looked on favorably, because they do the important work of moving labor along.

But, can there ever be too much of a good thing? Can you ever have too many contractions, or contractions that are so intense that they can be harmful to you or your baby?

Let’s look at what happens when you experience abnormal or excessive uterine contractions—specifically a type of abnormal contraction known as uterine tachysystole.

Understanding Uterine Tachysystole

What Is Uterine Tachysystole?

Uterine tachysystole is a term used to describe very frequent uterine contractions during labor.

In a 2013 research paper, the American College of Obstetricians and Gynecologists (ACOG) called upon physicians to stop calling these type of contractions “hyperstimulation” and “hypercontractility,” but urged them to adopt the term “tachysystole” (TS).

According to the ACOG, uterine tachysystole is defined as five contractions in a 10-minute time period.

Although uterine tachysystole can happen during any kind of labor, it is more frequently associated with births where labor stimulating medications are given.

More research is needed to get a fuller picture, but several studies have linked uterine tachysystole with fetal heart rate issues, placental abruption, increased likelihood of neonatal intensive care unit (NICU) stay, and reduced fetal oxygenation.

Uterine Tachysystole vs. Normal Contractions

In the weeks and months leading up to labor and delivery, you will experience several different types of contractions.

Before true labor starts, you will experience “practice” contractions known as false labor contractions or Braxton Hicks contractions. These types of contractions can be uncomfortable but they do not cause your cervix to dilate or your baby to move down the birth canal as true labor contractions do.

You know your contractions are “real” when they are more frequent, closer together, and when they happen on a regular basis (no stops and starts). In early labor, your contractions will generally be less painful, last for fewer minutes at a time, and be more spaced apart. As your labor progresses, your contractions will become more painful, last longer, and be spaced closer together.

You can picture contractions as an arc: they have a beginning, middle, and end, usually with a peak in pain and intensity in the middle. In between contractions, there are usually at least a few moments to rest. Even as labor intensifies, most labor contractions do not last more than 60 to 90 seconds, according to ACOG.

Uterine tachysystole is considered an excessively frequent contraction experience, with several contractions in a row during a short time period of time—five or six contractions within a 10-minute span. This leaves moms with very few moments to rest, and can put a strain on their bodies as well as their baby’s systems.

How Common Is Tachysystole?

Understanding uterine tachysystole is a field that researchers are just beginning to dive into, so data is limited. However, from the preliminary data that’s out there, uterine tachysystole may be more common than you realize.

For example, in ACOG’s research paper on uterine tachysystole, birthing moms of singleton babies from 10 Intermountain Healthcare hospitals were monitored from March 2007 to June 2009. 50, 335 deliveries took place among 48,529 women. Within that pool, there were 7,567 instances of uterine tachysystole observed.

Another study, published in The Journal of Maternal-Fetal & Neonatal Medicine, looked at uterine tachysystole among mothers who didn’t receive labor stimulating medicine. This study found that 11% of laboring moms had at least one episode of uterine tachysystole.

What Causes Tachysystole?

In the study published by ACOG of women who birthed in the Intermountain Healthcare hospital system, there were some factors that made them more likely to experience uterine tachysystole. These factors included:

  • Use of labor stimulating medication, such as oxytocin or misoprostol
  • Use of epidural for pain management
  • Induction of labor
  • Preeclampsia
  • Hypertension

In this study, women were twice as likely to experience an episode of uterine tachysystole if they had been given oxytocin during labor.

Risk Factors

Again, understanding uterine tachysystole and its effects of laboring women and babies is a relatively new field. So far, there are some reasons to be assured that experiencing a uterine tachysystole will not have a significant impact on you or your baby.

However, there are also some reasons to be concerned about uterine tachysystole.

Fetal Heart Rate Changes and Decreased Oxygen

In a 2012 study published in the American Journal of Obstetrics and Gynecology, uterine tachysystole was strongly associated with fetal heart rate decelerations. On the other hand, it wasn’t associated with poor or adverse outcomes for infants.

As the ACOG points out, increased contractions and uterine tachysystole events can lead to decreased oxygen to fetuses as well as changes in fetal heart rate. In their study of birthing women at Intermountain Healthcare hospitals, one fourth of all uterine tachysystole instances lead to fetal heart rate irregularities.

C-Section Births

The study published in the Journal of Maternal-Fetal & Neonatal Medicine found associations between uterine tachysystole and fetal heart rate issues. In addition, mothers who experienced uterine tachysystole were more likely to have a C-section birth, and their babies were more likely to need NICU care.

However, the study found that these babies were not more likely to have low Apgar scores at birth or show signs of meconium-stained amniotic fluid.

A Word From Verywell

If you are pregnant and concerned about uterine tachysystole or have had a prior experience with it during labor, you should discuss your concerns with your doctor or midwife.

If you or your baby had a poor outcome because of a uterine tachysystole, you will likely be very concerned about ensuring that this doesn’t happen again. Reducing your use of labor stimulating medication, where appropriate, might be something to discuss with your doctor.

Either way, remember that as patient and as a parent, you have a right to discuss your concerns with your healthcare providers, ask any questions that are on your mind, and advocate for the best possible outcome for you and your baby.

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4 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Heuser CC, Knight S, Esplin MS, et al. Tachysystole in term labor: incidence, risk factors, outcomes, and effect on fetal heart tracingsAmerican Journal of Obstetrics and Gynecology. 2013;209(1):32.e1-32.e6. doi:10.1016/j.ajog.2013.04.004.

  2. American College of Obstetricians and Gynecologists. How to tell when labor begins. Updated May 2020.

  3. Ahmed A, Aldhaheri S, Haberman S, Minkoff H, Sakr S, Zhu L. Uterine tachysystole in spontaneous labor at term. Journal of Maternal-Fetal & Neonatal Medicine. 2016;29(20):3335-3339. doi:10.3109/14767058.2015.1125463.

  4. Alexander J, Bleich A, Leveno K, Lo J, McIntire D, Stewart R. Defining uterine tachysystole: How much is too much?. American Journal of Obstetrics and Gynecology. 2012;207(4):290e1-290.e6. doi:10.1016/j.ajog.2012.07.032.

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